U.S. patent application number 12/046208 was filed with the patent office on 2008-07-03 for switch device, system, backup method and computer program.
This patent application is currently assigned to NEC CORPORATION. Invention is credited to Yoshihiro KAJIKI, Takashi TORII, Satoshi YAMAKAWA.
Application Number | 20080162608 12/046208 |
Document ID | / |
Family ID | 36146665 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080162608 |
Kind Code |
A1 |
TORII; Takashi ; et
al. |
July 3, 2008 |
SWITCH DEVICE, SYSTEM, BACKUP METHOD AND COMPUTER PROGRAM
Abstract
Disclosed is a system which includes at least one client, a
plural number of file servers, each having a file system, and a
switch logically arranged between the client and the plural file
servers to provide file access services which virtually render the
plural file services accessible as a single file system, termed a
`pseudo file system`, when viewed from the terminal. The switch
distributes a command for start of generation of snapshots to the
plural file servers, which file servers formulate respective
snapshots responsive to the command for start of formation of the
snapshots. The switch sets the plural snapshots, generated by the
plural file servers, so as to be associated with the file system
structure of the virtual file system at the time of formation of
the snapshots.
Inventors: |
TORII; Takashi; (Tokyo,
JP) ; YAMAKAWA; Satoshi; (Tokyo, JP) ; KAJIKI;
Yoshihiro; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
36146665 |
Appl. No.: |
12/046208 |
Filed: |
March 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11236844 |
Sep 28, 2005 |
|
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12046208 |
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Current U.S.
Class: |
1/1 ;
707/999.204; 707/E17.007; 707/E17.01 |
Current CPC
Class: |
G06F 16/1827 20190101;
G06F 11/1469 20130101; G06F 16/128 20190101; G06F 11/1456 20130101;
G06F 16/192 20190101; G06F 11/1466 20130101 |
Class at
Publication: |
707/204 ;
707/E17.007 |
International
Class: |
G06F 17/00 20060101
G06F017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2004 |
JP |
2004-284378 |
Claims
1. A backup management system comprising: a plurality of file
devices, each including a file system; means for halting access to
said file devices; and means for commanding said plurality of file
devices to start generation of snapshots after the access to said
file devices has halted.
2. The backup management system according to claim 1, further
comprising: means for restarting to access to said file devices
after completing generation of the snapshots.
3. The backup management system according to claims 1, further
comprising: a unit for consolidating the snapshots generated by
said plurality of file devices using junctions of said
snapshots.
4. A file access service system comprising: an intermediate device
logically arranged between at least one terminal and a plurality of
file devices, each provided with a file system; said intermediate
device including: means for halting access to said file devices;
and means for commanding said plurality of file devices to start
generation of snapshots after the access to said file devices has
halted.
5. The file access service system according to claim 4, further
comprising: means for restarting to access to said file devices
after completing generation of the snapshots.
6. The file access service system according to claims 4, further
comprising: a unit for consolidating the snapshots generated by
said plurality of file devices using junctions of said
snapshots.
7. A switch device logically arranged between at least one terminal
and a plurality of file devices, each provided with a file system,
said switch device including: means for halting access to said file
devices; and means for commanding said plurality of file devices to
start generation of snapshots after the access to said file devices
has halted.
8. The switch device according to claim 7, further comprising:
means for restarting to access to said file devices after
completing generation of the snapshots.
9. The switch device according to claims 7, further comprising: a
unit for consolidating the snapshots generated by said plurality of
file devices using junctions of said snapshots.
10. A method for backup management comprising: halting access to a
plurality of file devices, each provided with a file system; and
commanding said plurality of file devices to start generation of
snapshots after the access to said file devices has halted.
11. The method according to claim 10, further comprising:
restarting to access to said file devices after generating the
snapshots.
12. The method according to claims 10, further comprising:
consolidating the snapshots generated by said plurality of file
devices using junctions of said snapshots.
13. A method for file access service comprising: halting access to
a plurality of file devices, each provided with a file system; and
commanding said plurality of file devices to start generation of
snapshots after the access to said file devices has halted.
14. The method for file access service according to claim 13,
further comprising: restarting to access to said file devices after
completing generation of the snapshots.
15. The method for file access service according to claims 13,
further comprising: consolidating the snapshots generated by said
plurality of file devices using junctions of said snapshots.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a switch device logically arranged
between a client and file servers. More particularly, it relates to
a switch device in a system providing file access services to
plural file systems, as a virtual file system, as viewed from the
client, in which the switch device may efficiently carry out
snapshotting and backup/restore operations, and method as well as a
computer program for efficiently carrying out the snapshotting and
backup/restore operations.
BACKGROUND OF THE INVENTION
[0002] As a network storage system employing the NFS (Network File
System)/CIFS (Common Internet File System), as a protocol, and
which enables accessing the file systems from plural hosts, the NAS
(Network Attached System), for example, is currently used. The NAS
means a computer or a device co-owning files via NFS and CIFS.
[0003] Data recorded in a storage are periodically backed up on a
medium, such as a tape, in order to make it possible to restore
data for the possible case e.g. of occurrence of malfunctions. Of
these backed-up data, a snapshot is a read-only file system holding
an image of a file system structure at a certain point in time. By
taking the snapshot, a fixed image of the file system structure at
the time point of formation of the snapshot may be accessed, while
data at the time point of formation of the snapshot may be
restored, that is, the logical volume may be restored. For this
reason, the snapshot may be used as an example for taking
consolidated backup of the snapped file system. As for the
snapshot, reference may be had to e.g. the Patent Document 1 and
the Non-Patent Document 1. According to the present invention, the
processing for interlinking the plural snapshots is carried out, as
later explained. For aiding in the understanding of the relevant
technology, the snapshot will now be explained, based on the
description of the Patent Document 1. Meanwhile, in this Patent
Document 1, there is disclosed a method for managing a plurality of
snapshots in case these snapshots are supplied. With this method, a
series of metadata representing a file system are included in the
file system, so that snapshot of the file system will include
relevant metadata.
[0004] If an image of a file system structure at a certain point in
time has snapped a file system as shown for example in FIG. 13A, a
snapshot inode, shown for example in FIG. 13B, is generated as an
image of a file system structure at a certain point in time.
Meanwhile, the inode is a data structure for a file system layer to
specify a file. A snapshot inode is a replication of a root inode
of a file system structure and includes the pointer information to
an inode indirect block, an inode file data block and to file data
blocks A to C, as in FIG. 13A. Since the snapshot may be generated
by simply acquiring the pointer information, the time needed for
generating the snapshot is on the order of several seconds, even
for a large volume of data. If, after generating the snapshot, the
file data block C, for example, is changed, the inode file data
block, pointing to the so changed file data block, is changed to
reflect a new location C' of the so changed file data block (in the
case of WAFL (Write Anywhere File Layout)), as shown in FIG. 13C.
The snapshot inode includes a pointer pointing to the original
inode file system indirect block, while the inode file data block
includes pointers to the original file data blocks A to C. That is,
the snapshot holds a fixed image of the file system as of the
snapping time point. On the other hand, the newly written inode
file data block holds pointers to the file data blocks A and B and
the pointer information to the changed file data block C'. There is
also known a configuration in which, when a snapped file system is
subsequently changed, pre-change data, such as the file data block
C of FIG. 13C, is copied to a snapshot area, and in which, in
reading the snapshot, the changed original data, such as the file
data block C of FIG. 13C, for example, is read from the snapshot
(see e.g. Non-Patent Document 1).
[0005] If, after generation of a snapshot, a file is changed, the
inode structure of the file system may be restored to that at the
time point of snapshot generation, by accessing the snapshot inode.
More specifically, by following the pointers retained by the
snapshot inode, through the inode file indirect block and the inode
file data block, up to the unchanged file data blocks A to C, the
file system structure may be restored up to the state at the time
point of formation of the snapshot. It is noted that the `SNAPSHOT`
is a trademark owned by Network Appliance Inc. However, of course,
the `snapshot` in the context of the present specification is not
limited to the snapshot directed to the WAFL (Write Anywhere File
layout) of Network Appliance Inc. and means a fixed image of a file
system.
[0006] As for use of the snapshots, the date and time of snapshot
generation may be recorded, by way of generation management, and
plural snapshots may be managed within the same file system,
depending on the particular type of the snapshot forming software.
The file system structure snapped may be accessed via e.g. an
alias.
[0007] The basic configuration of the backup/recovery of the file
servers in the conventional network file system environment is the
individual backup/recovery by each file server. In this case, a
client accesses a file server, such as NAS, by e.g. an NFS
protocol, over a network, to make a remote login. Or, the client
makes a local login to take a backup on e.g. a local tape drive,
using CLI (Command Line Interface), such as rsh or ssh.
Alternatively, such a method may be used in which a backup server,
as a computer responsible for taking a backup, is NFS/CIFS mounted
to a file system of a backup client (file server computer), to take
a backup. Still alternatively, a backup client (file server) may be
connected to a backup server, using a protocol other than the NFS
protocol, such as SCSI (Small Computer System Interface), as with
the NDMP (Network Data Management Protocol) prescribing the
backup/recovery communication protocol between a primary storage
(storage for storing a file system currently in use) and a
secondary storage (storage for data retention), or a tape library
may be co-owned by plural file servers.
[0008] There is also known a configuration in which a switch 100',
virtually consolidating the resources of plural file servers 3, is
logically provided across the file servers 3 and the client 1, for
consolidating the plural file systems, in order to provide file
services of a virtually single system image, that is, SSI (Single
System Image), as shown in FIG. 14 (see e.g. Patent Documents 2 and
3, indicated hereinbelow). This switch 100' provides file services
of the single system image, such as a single NAS, by consolidating
and managing plural servers, without tampering with pre-existing
systems, provided only that the client and the server support the
standard protocol (NFS). Reference is also made to the disclosure
of, for example, the Patent Document 4, as a similar virtual file
system technique, a system for virtually unifying plural network
storages to a single storage, to enable accessing from the client
to, as it were, a single network storage. The system differs in
configuration from the switch 100' of FIG. 14.
[Patent Document 1]
[0009] JP Patent Kokai Publication No. JP-P2004-38929A
[Patent Document 2]
[0010] JP Patent Kokai Publication No. JP-P2003-203029A
[Patent Document 3]
[0011] JP Patent Kokai Publication No. JP-P2004-54607A
[Patent Document 4]
[0012] JP Patent Kokai Publication No. JP-P2003-345643A
[Non-Patent Document 1]
[0013] `HP JFS 3.3/HP OnlineJFS 3.3 VERITAS@ File System 3.3 System
Management Guide`, 4 Online Backup, p75 to 81
SUMMARY OF THE DISCLOSURE
[0014] By taking a snapshot, the file system at the snap time point
can be restored. In a file server, the backup/restore is a crucial
maintenance management operation, such that, depending on the
system management configuration, it is necessary to take snapshots
periodically every hour, every day, every week or every month to
hold hysteresis a preset number of times. In a conventional system,
snapshots and backup/restore are carried out from one file server
to another, and hence the management is complicated and a large
number of management steps is involved.
[0015] In the system shown in FIG. 4, the plural file systems are
hidden from the client 1 and virtualized as a single system, while
on-line data migration is carried out in combination to relieve the
load of the server administrator at the time of adding or replacing
file servers. However, the snapshot, backup and restore are carried
out individually, from one file server 3 to another, such that
cooperation among the devices is not presumed nor considered.
Although fairly acceptable management tools are supplied from
vendors of the file servers, such as NAS devices, these tools are
configured to output the status of the NAS or commands on a single
screen, while not supplying a technique of allowing the plural file
systems to look as a single file system, as with a virtual file
system.
[0016] If, in the system shown in FIG. 14, the snapshot and
backup/restore of the file systems are carried out separately from
one file system to another, the work load and the number of steps
are increased. Moreover, since the file systems are configured to
appear to the client as a single file system, through the switch
100', it is necessary for the administrator to take a mapping
between the virtual file system and the real file system, in taking
a backup, by onerous operations. If, in taking a backup, plural
file systems are backed up, without taking the mapping between the
plural file systems (real file systems), formed into a sole virtual
file system, and the virtual file system, recovery after
malfunctions encounters significant difficulties in restoring the
original virtual file system, because of lack of the mapping
information. In addition, if the administrator commits a mistake in
taking the mapping between the virtual file system and the real
file systems, significant difficulties are met in restoring the
virtual file system.
[0017] Thus, the present inventors have become aware of the fact
that, in a system which hides the plural file systems from the
client to allow the file systems to appear as a sole virtual file
system, it is desirable to implement integrated maintenance
management functions on the virtual file system level.
[0018] Accordingly, it is an object of the present invention to
provide a device, a system, a method for backup and restore, and a
computer program, in which the device is logically arranged between
plural file systems and a terminal to provide to the terminal
access services of an apparently single file system, corresponding
to plural real file systems, and in which the device has the
function of taking a backup and executing backup/recovery
management to improve maintenance, management performance,
reliability and safety.
[0019] The above and other objects are attained by the present
invention configured as follows:
[0020] In accordance with one aspect of the present invention,
there is provided a backup management system comprising:
[0021] a plurality of file devices, each including a file
system;
[0022] means for commanding said plurality of file devices to start
the generation of snapshots, which are fixed images of said file
systems at a certain point in time;
[0023] said plurality of file devices generating respective
snapshots responsive to a command for starting the generation of
said snapshots; and
[0024] means for setting a link across said snapshots to generate a
virtual snapshot so that said snapshots generated by said file
devices corresponds to a consolidated file system structure of said
file systems at the time of generation of said snapshots;
[0025] whereby backup or restore may be made using said virtual
snapshot.
[0026] According to the present invention, there is provided a file
access service system comprising:
[0027] at least one terminal;
[0028] a plurality of file devices, each including a file system;
and
[0029] an intermediate device logically arranged between said
terminal and said plurality of file devices, said intermediate
device supplying said terminal with a file access service which
allows said terminal to access said plural file systems as a single
file system, termed hereinafter a `pseudo file system`;
[0030] said intermediate device including means for commanding each
of said file devices to start generating a snapshot which is a
fixed image, at a certain point in time, of said file system of
each of said plurality of file devices;
[0031] each of said plurality of file devices generating a snapshot
responsive to a command from said intermediate device for starting
to generate the snapshot;
[0032] said intermediate device also including means for setting a
link across said plural snapshots so that a plurality of said
snapshots generated by said plurality of file devices correspond
said pseudo file system at the time of generation of said
snapshots.
[0033] Preferably, in the file access service system according to
the present invention, said intermediate device holds, as the
snapshot information corresponding to said pseudo file system, link
information of junctions connecting said snapshots.
[0034] Preferably, in the file access service system according to
the present invention, said intermediate device includes means for
exercising control for halting the access to said file systems in
starting to generate said snapshots.
[0035] Preferably, in the file access service system according to
the present invention, said intermediate device includes means for
exercising control for having snapshots generated by said file
devices after checking for synchronization in file accessing
between said file devices and said terminal.
[0036] Preferably, in the file access service system according to
the present invention, said intermediate device includes means for
exercising control for restarting the access to said file systems
after generation of said snapshots.
[0037] Preferably, in the file access service system according to
the present invention, said intermediate device assigns the same
generation name to each snapshot generation of said file
systems.
[0038] According to the present invention, the snapshot may be read
out by the terminal for taking backup.
[0039] According to the present invention, there may be provided a
device for taking a backup having an interface for communicating
with an intermediate device. The device for taking a backup
receives the information of the pseudo file system from the
intermediate device and associates the virtual file system with the
actual file system. The resulting information is backed up as a set
with backup data.
[0040] According to the present invention, the intermediate device
in restoration determines the destinations for restoration of the
file systems, based on the pseudo file system information.
[0041] According to the present invention, the device for taking a
backup restores the file systems, based on the pseudo file system
information, it backs up, and further restores the virtual file
system information on the intermediate device.
[0042] Preferably, in the file access service system according to
the present invention, the snapshots generated by said file devices
are read by said terminal to take backup of a backup image
corresponding to said snapshots in a recording device for
backup.
[0043] Preferably, in the file access service system according to
the present invention, there are further provided a backup control
device;
[0044] said backup control device receiving, in taking backup, a
plurality of file systems of said plural file devices, via said
intermediate device, to take a backup in a recording backup device
as a single virtual file system structure of said plural file
systems.
[0045] Preferably, in the file access service system according to
the present invention, in restoration, said backup control device
directly restores a single virtual file system of said plural file
systems from said recording backup device to a target file device
without the intermediary of said intermediate device.
[0046] Preferably, in the file access service system according to
the present invention, there are further provided a backup control
device for communication coupling to a plurality of said file
devices;
[0047] said backup control device having an interface for
communicating with said intermediate device;
[0048] said backup control device in taking a backup receiving
plural file systems of said plural file devices via said
intermediate device and taking a backup of said plural file systems
in said recording backup device as a single virtual file system
structure of said plural file systems.
[0049] Preferably, in the file access service system according to
the present invention, said backup control device in restoration
sends backup data of said recording backup device to said
intermediate device; and
[0050] said intermediate device distributes the backup data,
received from said backup control device, to a plurality of said
file devices for restoration, in keeping with the pseudo file
system information configured for allowing a plurality of said file
systems to look as a single file system.
[0051] Preferably, in the file access service system according to
the present invention, there is further provided a backup control
device for communication coupling to a plurality of said file
devices;
[0052] said backup control device having an interface for
communicating with said intermediate device;
[0053] said backup control device in taking a backup receiving
plural snapshots of said plural file devices via said intermediate
device; a link being set across said plural snapshots; said plural
snapshots, said link is set to, being backed up in said recording
backup device.
[0054] Preferably, in the file access service system according to
the present invention, said backup control device in restoration
sends the backup data of said recording backup device to said
intermediate device;
[0055] said intermediate device distributing and transmitting said
plural snapshots to said plural file devices;
[0056] said plural file devices restoring the file systems using
said snapshots transmitted thereto.
[0057] Preferably, in the file access service system according to
the present invention, there is further provided a backup control
device for communication coupling to a plurality of said file
devices;
[0058] said backup control device having an interface for
communicating with said intermediate device;
[0059] said backup control device in taking a backup receiving from
said intermediate device the pseudo file system information
configured for allowing a plurality of said file systems to look as
a single file system; said backup control device correlating said
pseudo file system information to the actual file systems to take a
backup of the so correlated information as a set with backup
data.
[0060] Preferably, in the file access service system according to
the present invention, in restoration, the backup data is
transferred from said recording backup device to a plurality of
said file devices, and wherein
[0061] said pseudo file system information is transmitted from said
backup control device to said intermediate device.
[0062] Preferably, in the file access service system according to
the present invention, said intermediate device is a switch device
logically arranged between said terminal forming a client and a
plurality of server devices each forming said file device;
[0063] said switch device receiving a file access request from said
client; said switch device distributing said file access request to
appropriate server devices and transmitting the so distributed file
access request; said switch device receiving a response to said
file access request transmitted from said server devices to
transfer said response to said terminal which transmitted said file
access request.
[0064] Preferably, in the file access service system according to
the present invention, said switch device includes
[0065] means for transmitting a request, pertinent to an object,
sent from said client, to said server device supervising said
object;
[0066] said means transmitting a response to said request from said
server device to said client as a source of transfer of said
request; said means inserting into the transmitted response the
server identification information for discriminating a server
device, supervising an object associated with an original object ID
generated in said server device, from other server devices, for
identifying said object, in case said original object ID is
included in the transmitted response, and rewriting said original
object ID to an information carrying object ID; said means in case
said information carrying object ID is included in the transmitted
request restoring said information carrying object ID into said
original object ID.
[0067] Preferably, in the file access service system according to
the present invention, said switch device stores and supervises, as
said pseudo file system information, the information pertinent to
nodes of directory trees of a unified single directory tree
combined from the directory trees of said plural file systems, as
said pseudo file system information.
[0068] Preferably, in the file access service system according to
the present invention, said server device is a NAS (Network
Attached Storage) device and wherein
[0069] said switch device allocates said file access request to
said servers using the predetermined layer information.
[0070] In another aspect, the present invention provides a method
for taking a backup in a file access service system, comprising at
least one terminal; a plurality of file devices, each including a
file system; and an intermediate device logically arranged between
said terminal and said file devices; said intermediate device
providing file access services which virtually render said plural
file services accessible as a single file system, termed a `pseudo
file system`, when viewed from said terminal; said method
comprising the steps of
[0071] said intermediate device distributing a command for starting
to generate a snapshot, as a fixed image of a file system at a
certain point in time, to a plurality of said file devices;
[0072] said plural file devices receiving a command for starting to
take snapshots from said intermediate device to formulate
respective snapshots; and
[0073] said intermediate device setting a link across a plurality
of said snapshots so that said snapshots generated by said file
devices are in correspondence with said pseudo-file system at the
time of generation of said snapshots.
[0074] Preferably, the backup method according to the present
invention, further comprises the steps of
[0075] said intermediate device holding the link information of
junctions connecting said snapshots as the snapshot information
corresponding to said pseudo-file system.
[0076] Preferably, the backup method according to the present
invention, further comprises the steps of
[0077] said intermediate device exercising control for halting the
access to said file systems in starting to take snapshots.
[0078] Preferably, the backup method according to the present
invention, further comprises the steps of
[0079] said intermediate device exercising control for first
confirming synchronization relating to file access across said file
devices and said terminal and for subsequently allowing said plural
file devices to take snapshots.
[0080] Preferably, the backup method according to the present
invention, further comprises the steps of
[0081] said intermediate device exercising control for first
generating snapshots and for subsequently restarting to access said
file systems.
[0082] Preferably, the backup method according to the present
invention, further comprises the step of
[0083] said intermediate device assigning the same generation name
to each snapshot generation of said file systems.
[0084] Preferably, the backup method according to the present
invention, further comprises the step of
[0085] reading out the snapshots generated by said file devices by
said terminal to take backup of backup images corresponding to said
snapshots in a recording device for backup.
[0086] Preferably, the backup method according to the present
invention, further comprises the step of
[0087] providing a backup control device;
[0088] said backup control device receiving, in taking backup, a
plurality of file systems of said plural file devices, via said
intermediate device, to take a backup of said file systems in a
recording backup device as a single virtual file system structure
of said plural file systems. In a method for restoration according
to the present invention,
[0089] in restoring data backed up by the back up method, said
backup control device directly restores a single virtual file
system of said plural file systems from said recording backup
device to a target file device without the intermediary of said
intermediate device.
[0090] Preferably, the backup method according to the present
invention, further comprises
[0091] providing a backup control device for communication coupling
to a plurality of said file devices and to said intermediate
device;
[0092] said backup control device in taking a backup receiving
plural file systems of said plural file devices via said
intermediate device and taking a backup of said plural file systems
as a single virtual file system structure of said plural file
systems in said recording backup device. In a method for restoring
data backed up by the said method comprises the steps of
[0093] said backup control device in restoration sending backup
data of said recording backup device to said intermediate device;
and
[0094] said intermediate device distributing the backup data to a
plurality of said file devices, for restoration, based on the
pseudo file system information configured for allowing a plurality
of said file systems to look as a single file system.
[0095] Preferably, the backup method according to the present
invention, further comprises
[0096] a backup control device for communication coupling to a
plurality of said file devices;
[0097] said backup control device in taking a backup receiving
plural snapshots of said plural file devices via said intermediate
device; a link being set across said plural snapshots; said plural
snapshots, said link is set to, being backed up in said recording
backup device. In the method for restoration of data backed up by
the method, said backup control device in restoration of the backed
up data sends the snapshots of said recording backup device to said
intermediate device;
[0098] said intermediate device distributing and transmitting said
plural snapshots to said plural file devices;
[0099] said plural file devices restoring the file systems based on
said snapshots transmitted thereto.
[0100] Preferably, the backup method according to the present
invention, further comprises
[0101] providing a backup control device for communication coupling
to a plurality of said file devices;
[0102] said backup control device in taking a backup receiving from
said intermediate device the pseudo file system information
configured for allowing a plurality of said file systems to look as
a single file system; said backup control device correlating said
pseudo file system information to the actual file systems to take a
backup of the so correlated information as a set with backup data.
In the method for restoration of data backed up by the back up
method, in restoration, the backup data is transferred from said
recording backup device to a plurality of said file devices, and
wherein
[0103] said pseudo file system information is transmitted from said
backup control device to said intermediate device.
[0104] Preferably, in the backup method according to the present
invention, said intermediate device is a switch device logically
arranged between said terminal forming a client and a plurality of
server devices each forming said file device;
[0105] said switch device receiving a file access request from said
client; said switch device distributing said file access request to
appropriate server devices and transmitting the so distributed file
access request; said switch device receiving a response to said
file access request transmitted from said server devices to
transfer said response to said terminal which transmitted said file
access request.
[0106] Preferably, in the backup method according to the present
invention, said switch device transmits a request, pertinent to an
object, sent from said client, to said servers supervising said
object;
[0107] a response to said request from said server device is
transmitted to said client as a source of transfer of said request;
and wherein the server identification information for
discriminating a server device, supervising an object associated
with an original object ID generated in said server device, from
other server devices, is inserted into a transmitted response, for
identifying said object, in case said original object ID is
included in the transmitted response, and said original object ID
is rewritten to an information carrying object ID; said information
carrying object ID being restored into said original object ID in
case said information carrying object ID is included in the
transmitted request.
[0108] Preferably, in the backup method according to the present
invention, said switch device stores and supervises, as said pseudo
file system information, the information pertinent to nodes of
directory trees of a unified single directory tree combined from
the directory trees of said plural file systems, as said pseudo
file system information.
[0109] Preferably, in the backup method according to the present
invention, said server device is a NAS (Network Attached Storage)
device and wherein said switch device distributes said file access
request to said servers using the predetermined layer
information.
[0110] According to yet another aspect of the present invention,
there is provided a switch device logically arranged between at
least one client and a plurality of file servers, each provided
with a file system, for providing file access services which
virtually render said plural file systems accessible as a single
file system, termed a `pseudo file system`, when viewed from said
client; said switch device comprising
[0111] means for distributing a command for starting to generate a
snapshot, as a fixed image of a file system at a certain point in
time, to a plurality of said file servers; and
[0112] means for setting a link across a plurality of said
snapshots so that said snapshots generated by said file servers on
receipt of a command for staring to generate the snapshots so that
said snapshots are in correspondence with said pseudo-file system
at the time of generation of said snapshots.
[0113] Preferably, in the switch device according to the present
invention, the link information of junctions connecting said
snapshots is retained as the snapshot information corresponding to
said pseudo-file system.
[0114] Preferably, the switch device according to the present
invention, further comprises means for exercising control for
halting the access to said file systems in starting to take
snapshots.
[0115] Preferably, the switch device according to the present
invention, further comprises means for exercising control for first
confirming synchronization relating to file access across said file
servers and said client and for subsequently allowing said plural
file devices to take snapshots.
[0116] Preferably, the switch device according to the present
invention, further comprises means for exercising control for first
generating snapshots and for subsequently restarting to access said
file systems.
[0117] Preferably, in the switch device according to the present
invention, the same generation name is assigned to each snapshot
generation of said file systems.
[0118] According to another aspect of the present invention, there
is provided a computer program for a computer constituting a switch
device logically arranged between at least one client and a
plurality of file servers, each provided with a file system, for
providing file access services which virtually render said plural
file systems accessible as a single file system, termed a `pseudo
file system`, when viewed from said client, said program causing
said computer to execute the processing of distributing a command
for starting to generate a snapshot, as a fixed image of a file
system at a certain point in time, to a plurality of said file
servers; and
[0119] setting a link across a plurality of said snapshots so that
said snapshots generated by said file servers on receipt of a
command for snapshotting to generate the snapshots so that said
snapshots are in correspondence with said pseudo-file system at the
time of generation of said snapshots.
[0120] Preferably, in the program according to the present
invention, the link information of junctions connecting said
snapshots is retained as the snapshot information corresponding to
said pseudo-file system.
[0121] Preferably, the program according to the present invention,
further comprises the processing of exercising control for halting
the access to said file systems in starting to take snapshots.
[0122] Preferably, the program according to the present invention,
further comprises the processing of exercising control for first
confirming synchronization relating to file access across said file
servers and said client and for subsequently allowing said plural
file devices to take snapshots.
[0123] Preferably, the program according to the present invention,
further comprises the processing of exercising control for first
generating snapshots and for subsequently restarting to access said
file systems.
[0124] Preferably, the program according to the present invention,
the same generation name is donated to each snapshot generation of
said file systems.
[0125] The meritorious effects of the present invention are
summarized as follows.
[0126] According to the present invention, there is provided a
system for supporting file system access services to a virtualized
file system for plural real file systems, in which an administrator
is able to manage the snapshotting and backup/restore as a
virtualized device, whereby the number of management steps may be
decreased appreciably.
[0127] Still other objects and advantages of the present invention
will become readily apparent to those skilled in this art from the
following detailed description in conjunction with the accompanying
drawings wherein only the preferred embodiments of the invention
are shown and described, simply by way of illustration of the best
mode contemplated of carrying out this invention. As will be
realized, the invention is capable of other and different
embodiments, and its several details are capable of modifications
in various obvious respects, all without departing from the
invention. Accordingly, the drawing and description are to be
regarded as illustrative in nature, and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0128] FIG. 1 is a diagram showing system configuration of an
embodiment of the present invention.
[0129] FIG. 2 is a diagram showing configuration of a switch of an
embodiment of the present invention.
[0130] FIG. 3 illustrates a unified directory tree in an embodiment
of the present invention.
[0131] FIG. 4 illustrates generation of a snapshot in an embodiment
of the present invention.
[0132] FIG. 5 illustrates the sequence of generation of a snapshot
in an embodiment of the present invention.
[0133] FIG. 6 illustrates backup/restore in an embodiment of the
present invention.
[0134] FIG. 7 illustrates a processing sequence for backup/restore
in an embodiment of the present invention.
[0135] FIG. 8 is a diagram showing system configuration of another
embodiment of the present invention.
[0136] FIG. 9 illustrates backup/restore in another embodiment of
the present invention.
[0137] FIG. 10 illustrates a processing sequence for backup/restore
in another embodiment of the present invention.
[0138] FIG. 11 illustrates backup/restore in another embodiment of
the present invention.
[0139] FIG. 12 illustrates a processing sequence of for
backup/restore in a further embodiment of the present
invention.
[0140] FIGS. 13A, 13B and 13C illustrate snapshot.
[0141] FIG. 14 illustrates a conventional system configuration.
PREFERRED EMBODIMENTS OF THE INVENTION
[0142] An embodiment of the present invention will now be
described. Referring to FIG. 1, a system according to an embodiment
of the present invention includes a switch 100 which is logically
arranged between the client 1 and the file devices. The switch 100
provides file access services which virtually render the plural
file services accessible as a single file system, termed a `pseudo
file system`, when viewed from the terminal. The switch has the
function of performing integrated management of the snapshotting
and backup/restoring of plural file systems, as a single virtual
file system.
[0143] A snapshot command is entered to the switch 100. This
inputting is achieved by a command over a network 2, or login at
the switch 100.
[0144] The switch 100 receives the snapshot command and distributes
the command to a plurality of file servers 3 to take respective
snapshots. Each file server 3 is assumed to be provided with
snapshot function.
[0145] With the switch 100, it is possible to halt file access in
timed relation to the snapshotting (to freeze the snapped file
system) and to take a point of quiescence (check point) of the
virtual file system.
[0146] The switch 100 then sets a link across the snapshots of the
respective file systems, in accordance with a consolidated
directory tree, corresponding to a single file system (termed a
pseudo file system), obtained by virtualizing plural file systems
with the link set across the plural snapshots, the plural snapshots
are virtualized in accordance with the pseudo file system. The
switch 100 manages the information for virtualization of snapshots.
In this manner, data of the plural snapshots may be made to
coincide with data of the pseudo file system.
[0147] The switch 100 also donates, for management, the same
generation name by a command to the snapshots of the same
generation of the file systems of the respective servers 3.
[0148] Next, backup taking by the snapshots will be described. If,
in taking a backup to a backup unit 6, a client 1, for example,
takes a backup over the network 2, the client reads out the
snapshots from the plural file servers 3. At this time, the client
1 is able to read out, via switch 100, a plural number of
virtualized snapshots. A backup image of the pseudo file system
structure at the time point of generation of the virtualized
snapshots is backed up on a recording medium, such as tape. That
is, according to the present invention, a virtualized snapshot
structure is formed by plural snapshots by the switch 100 setting a
link across plural snapshots. Since the structure of the
virtualized snapshots coincides with the file system structure of
the pseudo file system as of the snapshotting time point, the
pseudo file system as of the snapshotting time point can be backed
up and restored. This represents a principal feature of the present
invention.
[0149] In taking backup to a tape drive unit, not shown, locally
connected to the file server, or in taking backup with NDMP
(Network Dump Management Protocol) or SCSI (Small Computer System
Interface), a backup server 7 takes backup of each file server 3,
as shown in FIG. 8.
[0150] The backup server 7 includes an interface (71 of FIG. 8),
configured for cooperating with the switch 100. The pseudo file
system information for turning real file systems into a sole
virtual file system that looks as a single file system is delivered
from the switch 100 to the backup server 7.
[0151] The backup server 7 correlates the pseudo file system
information with the servers 3 and takes a backup of the so
correlated pseudo file system information as a set with data files
on tape drives 8.
[0152] Thus, according to the present invention, it is possible to
take backup in accordance with the unified directory tree of the
pseudo file system. In the conventional system, an administrator
has to map the pseudo file system information with the real file
systems to take a backup, as described above. This operation may be
eliminated with the present invention.
[0153] The restoring operation according to the present invention
will be described. In case backup has been stored in the backup
unit 6 through the client 1, in FIG. 1, a backup image, coincident
with the file system structure of the pseudo file system, is stored
in the backup unit 6, as described above. Thus, in restoring the
backup image in the sole file server 3, the switch 100 does not
take part in the restoring operation. That is, the backup image is
directly restored from the backup unit 6 to the file server 3,
operating as a target. Of course, the client 1 may access the
restored file system via switch 100. The correspondence between the
objects of the file system and the servers for storing the objects
is supervised by the switch 100, and file access requests from the
client are allocated via switch 100 to relevant servers 3.
[0154] If, in the restore operation, the pseudo file system,
supervised by the switch 100, is restored to plural file servers 3,
the switch determines the restore destinations for the backup data,
based on the pseudo file system information corresponding to the
backup image. This restores file systems, corresponding to the
consolidated directory trees, at the time point of formation of the
snapshots.
[0155] In case backup is taken with the protocol other than the NFS
protocol, such as NDMP or SCSI, a backup server 7 restores the file
systems to the file servers 3, based on the pseudo file system
information, as shown in FIG. 8. The backup server 7 restores the
pseudo file system information, backed up to the tape drives 8, to
the switch 100. In this manner, the pseudo file system at the time
point of the snapshotting may be regenerated via switch 100.
[0156] Thus, in a network file system, formed into a single file
system, as a virtual file system, from the plural file systems, in
an embodiment of the present invention, an administrator may
comprehensively supervise snapshotting and backup/restore as a
virtual device, thereby significantly reducing the number of
management steps. In the following, explanation is made with
reference to preferred embodiments of the present invention.
[0157] FIG. 1 shows the configuration of a network file system, as
a client-server remote file system, provided with a switch
according to an embodiment of the present invention. Referring to
FIG. 1, the network file system includes at least one client 1, at
least one file server 3 and a switch 100, all connected to a
network 2. The server 3, which includes a file system layer 4
composed by software for managing data, such as files, accessed by
file access services, and a storage device 5 for storing data and
files, is a file server providing file access services to each
client. A backup unit 6 is connected to the network 2 to save
backup data of the servers 3. In the present embodiment, the switch
100 is provided with the function of managing snapshot and
backup/restore in the servers 3. As shown for example in FIG. 6,
regarding the backup unit 6, a backup server 7 may be connected to
the network 2 and to the file servers 3 so that backup will be
carried out from the backup client (file server 3) via backup
server 7 to tape drives 8.
[0158] As a basic technology for hiding the presence of the plural
servers 3 from the client 1, the management of the correspondence
relationship between the object ID and the server 3 in the switch
100 is first described. As for details, see e.g. the above
indicated Patent Document 2. The switch 100 receives a file access
request from the client 1 and distributes and transmits the request
to appropriate ones of the file servers 3. On the other hand, the
switch 100 receives a response for the file access request,
transmitted from the file servers 3, to transfer the response to
the associated client as the source of transfer of the file access
request. The client 1 designates an ID for identification of
objects, such as directories or files, being accessed, and accesses
the object that are managed by the servers 3. The object ID is
generated in the server 3 and the client 1 owns a list of the
objects that the client is able to access. The client generates and
transmits a request designating the access path to the object from
the above list, and retrieves the object ID of the object, that may
be accessed first, from the response data. As for the object,
arranged in a lower rank relative to the object, the object ID of
which has already been acquired by the client 1, the client 1
transmits a request, inclusive of the object ID, already retrieved,
and the name of the object, as a target of the file access, and
retrieves the object ID from the response to the request.
[0159] In the network file system of the present embodiment, the
presence of the server 3 is hidden from the client by the switch
100. Thus, a request for file access from the client 1 is
transmitted to the switch 100. On receipt of the file access
request from the client 1, the switch 100 distributes and transfers
(routes) the file access request to an appropriate server 3. The
switch 100 receives a response to the file access request,
transmitted from the server 3, and transmits (routes) the response
to the client 1 which transmitted the file access request. The
object ID, generated in the server 3, is made up by a data string
that can be interpreted only by the server 3 which produced it, so
that neither the client 1 nor the switch 100 is able to interpret
the object ID data. Moreover, the client 1 is unable to manipulate
the object, matched to the object ID, except if the client 1 has
received the response from the server 3 and has obtained the object
ID contained in the response. Thus, in the present embodiment, the
switch 100 inserts server identification information for
identifying the server, as the source of transfer, from the other
server(s), into the object ID, included in the response data
transmitted from the server 3, reconstructs a packet, by a
response, including the object ID, in turn including the so
inserted server identification information, and re-transmits the so
reconstructed packet to the client. The client 1 transmits the file
access request which includes the object ID into which has been
inserted the server identification information, to the switch 100.
The switch 100 receives the file access request transmitted from
the client and refers to the server identification information,
inserted in the object ID thereof, to specify the server to which
the file access request is to be transmitted. Meanwhile, when
transmitting the file access request to the server 3, the switch
100 converts the object ID, into which has been introduced the
server identification information, to the original object ID
generated by the server 3. With the switch 100, having the function
above mentioned, it is possible to achieve distributed processing
by plural servers in the network file system.
[0160] FIG. 2 illustrates an example of the configuration of the
switch 100 according to the present embodiment. Referring to FIG.
2, the switch 100 according to the present embodiment includes an
object ID rewrite unit 101 for rewriting the object ID, as
described above, a file access management unit 102, a packet
processing unit 103, a file system supplementary processing unit
104, a pseudo-file system (PFS) 105, a virtual snapshot management
unit 106 and the virtual snapshot link information 107.
[0161] The packet processing unit 103 analyzes a packet, received
over the network 2 from the client 1 and the servers 3, extracts
data contained in the packet and outputs the data to the file
access management unit 102. The packet processing unit 103
packetizes the data output from the file access management unit
102, and transmits the so packetized data over the network 2 to the
client 1 and to the servers 3.
[0162] The file access management unit 102 is supplied with and
analyzes data, output from the packet processing unit 103, and
determines the transfer destination of the packet 103 received by
the packet processing unit 103.
[0163] The object ID rewrite unit 101 rewrites the object ID,
contained in the above data, depending on the transfer destination
of the packet as determined by the file access management unit
102.
[0164] The pseudo-file system 105 is a system for combining plural
directory trees, made up by respective file systems of the plural
servers 3, shown in FIG. 1, and for managing the directory trees,
thus combined together, as a consolidated directory tree.
[0165] The file system supplementary processing unit 104 executes
supplementary processing in a case where a file access request from
the client 1 necessitates file access across a plurality of
transmission destinations such as the plurality of servers 3 or
plurality of file system layers 4.
[0166] The virtual snapshot management unit 106 issues a snapshot
command to the server 3. The virtual snapshot management unit 106
also exercises control for setting a link across the plural
snapshots in correspondence with the file system structure of the
pseudo-file system (PFS) 105 at the time of generating snapshots.
Meanwhile, in the present embodiment, it is each server 3 that
takes charge of snapshot, backup and restore processing
operations.
[0167] The virtual snapshot management unit 106 sets up the link
across the plural snapshots generated by the plural servers 3, so
that these snapshots will be in correspondence with the
consolidated directory tree of the pseudo-file system 105. The
virtual snapshot link information 107 saves and holds the link
information across the snapshots (pointer information at a junction
to the connection destination). Although the pseudo-file system 105
of the switch 100 is changed with changes in the data in the
servers 3, the virtual snapshot link information 107 is a fixed
image of the virtual snapshots at the time the snapshots were
prepared. Thus, the pseudo-file system 105 at the time of the
preparation of the snapshots may be restored based on the virtual
snapshot link information 107.
[0168] In the present embodiment, the switch 100, configured to
hold and manage the information at junctions of the directly tree
of the respective servers 3, in the pseudo-file system 105, is also
configured to hold and manage the information at the junctions of
the snapshots of the respective servers 3. The virtual snapshot
link information 107 is supervised in dependence upon the snapshot
generation. That is, virtual snapshot link information 107 for a
predetermined number of generations is saved and retained.
[0169] The switch 100 includes, in addition to the function of
appropriately distributing the file access request packets and file
access response packets to the client 1 or to the servers 3, the
function of consolidating the directory trees, formed in the file
systems 4 of the plural servers 3, to a single directory tree of
the pseudo-file system 105. With this function of the switch 100,
the client 1 can access any file in the plural servers 3, in a
manner as if the client is accessing only the pseudo-file system
105 of the switch 100, without the client becoming conscious of the
presence of the individual file systems 4 in the plural servers
3.
[0170] The pseudo-file system 105 combines the tree structures of
the plural directory trees on the file systems 4, laid open by the
servers 3 as being accessible over the network 2, for mapping the
tree structures to a single directory tree. In the present
embodiment, the processing and functions of the object ID rewrite
unit 101, file access management unit 102, packet processing unit
103, file system supplementary processing unit 104 and the virtual
snapshot management unit 106 of the switch 100, shown in FIG. 2,
may be implemented by a computer program executing on a computer
constituting the switch 100.
[0171] FIG. 3 shows an example of a directory tree 200 of the
pseudo-file system 105 of FIG. 2. Referring to FIG. 3, the
pseudo-file system 105 maps tree structures of directory trees of a
directory b(221), laid open by a server 3A, and a directory c(222),
laid open by a server 3B, to a directory tree of sub-directories
from a root directory 220(/) formed on the pseudo-file system 105.
The root directory 220(/) of the directory tree 220 formed on the
pseudo-file system 105 includes pointers to the directories 221 and
222. The pseudo-file system 105 creates the directory tree 200 of
the pseudo-file system by registering the tree structure of the
directory tree of the directory e(224), laid open in the server B,
as a directory tree of subdirectories of a directory f(223) lying
in a lower layer of the directory tree of the directory b (221).
With the switch device according to the present embodiment, the
names of the directories on the directory tree 200 of the
pseudo-file system need not necessarily be the same as the
directory names as set in the file systems 4 of the servers 3, such
that these directories may be renamed and these different names may
be laid open to the client.
[0172] In the switch 100, the pseudo-file system 105 manages only
the tree structure of the directory tree 200 of the pseudo-file
system, such that, for example, the object data, attribute
information or the tree structure of each file system, other than
the junctions thereof, are all supervised by the server 3. For
example, the pseudo-file system retains and supervises the tree
information of the directory tree 200 of the pseudo-file system of
FIG. 3, such as the information on the node junction points of the
root directory 220(/). Only the tree information of the junctions
in the directory tree 200 of the pseudo file system at the time of
the snapshot generated is stored and supervised as the virtual
snapshot link information 107 of FIG. 2, while each tree structure
other than the junctions is stored as the snapshot of the server 3.
This configuration represents an essential feature of the present
invention.
[0173] The switch 100 takes charge only of name resolution
processing for tree portions interconnecting the file systems 4,
while the server 3 takes charge of processing for other tree
portions, that is, tree portions other than junctions.
[0174] A concrete example of the operation of the present
embodiment will now be described. FIG. 4 schematically shows the
operation of an embodiment of the present invention. In FIG. 4, a
virtual snapshot function 110 corresponds to the virtual snapshot
management unit 106 of FIG. 2, whilst a switch
function/virtualization management function 120 comprises the
packet processing unit 103, file access management unit 102, file
system supplementary processing unit 104, pseudo-file system 105
and the virtual snapshot link information 107 of FIG. 2. In the
following, the server is assumed to be a NAS device, only by way of
an example.
[0175] The switch 100 receives a command for generating a snapshot
(step 1). In the present embodiment, a command for generating a
snapshot is issued by log-in at the switch 100 or over the network.
Or, a command for generating the snapshot may periodically be
issued by the switch 100.
[0176] The virtual snapshot function 110 commands the switch
function/virtualization management function 120 to halt the
forwarding to prohibit updating of the file system being snapped
(step 2). For finding a complete point of quiescence of the file
system being snapped, it is confirmed at this time that a response
from the server 3 to the request (Call) from the client 1 has been
returned (checking for synchronization). If synchronization is not
achieved, the command for starting the generation of a snapshot to
the server 3 is set in the waiting state. This synchronization
management is carried out by cooperation between the file access
management unit 102 and the packet processing unit 103 of FIG.
2.
[0177] The virtual snapshot function 110 notifies the servers 3A
and 3B accommodating the snapshot function (NAS servers) of the
start of generation of the snapshot (step 3).
[0178] On receipt of the completion of the formation of the
snapshot by the server 3, the virtual snapshot function 110
commences the forwarding to the switch function/virtualization
management function 120.
[0179] After generating the snapshot in the servers 3A and 3B, a
link for the pseudo-file system 105 (PFS link) is created in the
pseudo-file system 105 in the switch 100 (step 105). For example,
if the directory tree 200 of the pseudo file system is as shown at
200 in FIG. 4 (or 200 in FIG. 3), that is, if the directory tree
200 is unified from the directory tree 201 of the file system of
the server 3A and the directory tree 202 of the file system of the
server 3B, the servers 3A and 3B on receipt of the notification of
the start of the formation of the snapshot generate an image of the
directory tree 201 as `snapshot A.1` and an image of the directory
tree 202 as `snapshot B.1`, respectively, where `snapshot A`
denotes an alias name for snapshot access, as set on the system,
and `1` denotes the generation number. It is noted that the alias
names `snapshot A` and `snapshot B` are simply for matching to the
servers 3A, 3B, such that the alias names of the snapshots, as set
by the servers' snapshot software, may be the same for the
different servers.
[0180] In the directory tree 200 of the pseudo-file system 105 of
the switch 100, the directory tree 201 of the real file system
(server 3A) is linked (by PFS link) to the directory tree 202 of
the real file system (server 3B). In similar manner, the snapshot
`snapshot A.1` of the directory tree 201, generated by the server
3A, is linked by an equivalent link (PFS link) to the snapshot
`snapshot B.1` of the directory tree 201, generated by the server
3B. Specifically, the pointer information, pointing to the objects
of the link destination, is held at the junction between the two
snapshots `snapshot A.1` and `snapshot B.1`. This linkage
information is stored and managed by the switch 100, as the virtual
snapshot link information 107, in accordance with the snapshot
generation.
[0181] In this manner, the plural snapshots, discretely generated
in the respective servers 3 of FIG. 1, may automatically be mapped
to a consolidated directory tree effective at the time of the
formation of the plural snapshots.
[0182] FIG. 5 illustrates a processing sequence of the present
invention, shown in FIG. 4. The servers are NAS servers. The switch
100 receives a command for generating a snapshot (step 1).
[0183] The virtual snapshot function 110 commands the switch
function/virtualization management function 120 to halt forwarding
to inhibit the updating of the file system structure of the servers
3A, 3B. The switch function/virtualization management function 120
halts the forwarding and verifies the synchronization. For example,
the switch function/virtualization management function verifies
that no response to a call from the client has been returned from
the servers 3A and 3B.
[0184] The virtual snapshot function 110 of the switch 100 sends
notification of snapshot generation to the snapshot accommodating
servers (NAS servers) 3A and 3B under its control (step 3). This
notification is carried out by the switch 100 executing the snap
shot command by the server 3 by a rsh (remote shell) or ssh (secure
shell). Meanwhile, the virtual snapshot function 110 may transmit
snap shot commands in a parallel fashion to a larger number of
snapshot accommodating servers.
[0185] The switch 100 may assign the name of the same generation
for the snapshot generation of the servers 3A and 3B. In this case,
the generation name may be attached to the notification of the
snapshot generation from the switch 100.
[0186] The virtual snapshot function 110 commands the switch
function/virtualization management function 120 to restart the
forwarding (step 4).
[0187] The switch function/virtualization management function 120
creates a link across the plural snapshots in correspondence with
the pseudo-file system 105. After creating the link, the switch
function/virtualization management function 120 transmits the
response to the virtual snapshot function 110, which virtual
snapshot function 110 then transmits an accept response (accept) to
a terminal.
[0188] FIG. 6 illustrates the backup/restore operation with a
pseudo file system image according to an embodiment of the present
invention. The snapshots (snapshot A and snapshot B) of two file
systems are combined by a link (PFS link). In this state, an image
which is the same as each snapshot is read out from each of the two
file systems and backed up under control by the switch of FIG. 1.
Thus, a backup image of a single virtual file system associated
with plural file systems, is saved in e.g. a tape. Meanwhile, in
FIG. 6, `Production Data` schematically represents real data
modified as from the time of generation of the snapshots (snapshot
A and snapshot B).
[0189] The backup employing the snapshot will now be described.
Since snapshot data are the same as data of the snapped file
system, a backup command, such as cpio, operating based on a
standard file system structure, may be used. With the backup
command for reading a raw disk image, such as fscat, a raw image of
the file system, which is the same as that obtained when the backup
command of the disk image is used for the disk which has stored the
file system snapped at the time of the generation of the snapshot,
is obtained. If a system call which supports reading of the
snapshot is used, the same result as that obtained on reading the
disk which stored the snapped file system when the snapshot was
generated may be obtained (see e.g. the above indicated Non-Patent
Document 1).
[0190] When the backup image, saved on a tape, is restored in a
single file system, the one virtual file system for the time point
of formation of the snapshot, may directly be restored.
[0191] The processing of FIG. 6 may also be carried out by the
client 1 of FIG. 1 being mounted to the server 3 via switch 100, in
accordance with the NFS protocol, reading out the snapshot and
backing up the snapshot in the backup unit 6.
[0192] FIG. 7 illustrates the case of carrying out the operation of
FIG. 6 using a backup server. A snapshot is taken by each of the
two file servers 3 (NAS#1, NAS#2), and the switch 100, termed a NAS
switch, sets a link across plural snapshots of the two file servers
3 (NAS#1, NAS#2). The respective file systems of the two file
servers 3 (NAS#1, NAS#2) are backed up on the tape drives 8, via
switch 100 and backup server 7, to the same image as the
virtualized snapshot. This backs up a backup image (i.e. a backup
image of a virtual file system) of the plural file systems, turned
into a single virtual file system. This configuration also
represents one of the principal features of the present
invention.
[0193] In restoring, the backup image is restored from the tapes 8
to a single file server 3 (NAS device), by the backup server 7,
without the intermediary of the switch 100. The file server 3 is
able to restore the virtual file system as of the snap time
point.
[0194] In the present embodiment, the backup server and the file
server may be connected with a protocol other than the NFS protocol
to effectuate high-speed transfer. The storage device for backup is
not limited to a tape. Of course, the storage device for backup is
not limited to a tape drive and may be any of other suitable
recording devices.
[0195] FIG. 8 shows an example of the configuration of a system
including the backup server 7 shown in FIG. 7. The backup server 7
and the server 3 (backup client) may also be connected by an
interface other than the NFS protocol (e.g. SCSI). The backup
server 7 and the switch 100 may also be connected by an interface
other than the NFS protocol. There may also be provided an
interface 71 for controlling the direct communication connection
across the backup server 7 and the switch 100.
[0196] FIG. 9 illustrates the operation for backup/restore to the
image of the pseudo file system for another embodiment of the
present invention. A link (PFS link) is set across the snapshots of
the two file systems (snapshotA, snapshotB), in keeping with the
directory tree of the pseudo file system. In this state, the backup
of the two file systems is taken, using virtualized snapshots. A
backup image of the directory tree of the pseudo file system at the
time point of the generation of the snapshots is stored e.g. in a
tape. Meanwhile, the "production data" in FIG. 9 schematically
shows the real data changed as from the time point of the
generation of the snapshots.
[0197] The switch 100 distributes the backup image, stored on the
tape, to restore destinations, based on the pseudo-file system
information of the switch 100 (virtual snapshot link information
107 of FIG. 2), to restore the image to the two file systems, for
restoration of the file system at the time point of snapshot
generation, in the respective file systems. By the restored two
file systems, the virtual file system at the time of snapshot
generation may be restored.
[0198] FIG. 10 schematically shows a case where the file server
(backup client), switch and the backup server execute the
processing, shown in FIG. 9, using the NFS protocol. The two file
servers 3 (NAS#1 and NAS#2) take snapshots and the switch 100 (NAS
switch) sets a link across the plural snapshots, in correspondence
with the directory tree of the pseudo file system, to generate a
virtualized snapshot. The backup server 7 is mounted via switch 100
to the file servers 3 to take a backup using the snapshots. At this
time, the data read out from the two file servers 3 (NAS#1, NAS#2)
are backed up in the tape drives 8, in accordance with the
snapshots turned into the virtual entities by the switch (NAS
switch 100), for taking a backup of the file system corresponding
to the file system structure of the pseudo file system.
[0199] In restoring, backup data are distributed from the backup
server 7 via switch 100 to plural file servers (NAS devices). The
restore data (objects) are distributed, at the time of restoring,
to the servers 3 by the switch 100, as it is verified, based on the
virtual snapshot link information 107, in the configuration shown
in FIG. 2, to which server relates the restore data. As for the
backup data, increments (delta) as from the time of snapshot
generation may be backed up. In this case, the file system, added
by the increments as from the time point of the snapshot
generation, is restored in the two servers.
[0200] FIG. 11 illustrates backup/restore processing in case the
file server (backup client) and the backup server communicate with
each other using a protocol other than the NFS protocol. There is a
link (PFS link) formed across the snapshots of the two file systems
(snapshot A and snapshot B), in keeping with the directory tree of
the pseudo file system at the time of snapshot generation. In this
state, each of the two file systems is backed up and furthermore
the information of the pseudo-file system 105 at the time of
snapshot generation (directory tree information) is stored e.g. in
the tape.
[0201] By restoring the backup image of the two file systems of the
tapes 8, and by saving the pseudo-file system information at the
time of snapshot generation in the switch 100, the virtual file
system at the time of snapshot generation, when viewed from the
client 1, may be restored via switch 100.
[0202] FIG. 12 schematically shows the case where the file server
(backup client) and the backup server perform the processing shown
in FIG. 11 using a protocol other than the NFS protocol. The two
file servers 3 (NAS#1, NAS#2) take snapshots, whilst the switch 100
sets a link (PFS link) of the two snapshots.
[0203] From the two file servers 3 (NAS#1, NAS#2), data are
directly transmitted to the backup server 7, by e.g. SCSI, without
the intermediary of the switch 100, so as to be backed up e.g. in
the tapes 8. The backup server 7 may carry out the full backup of
the storage device to the tape 8.
[0204] From the switch 100, the pseudo file system information (PFS
information), for example, the virtual snapshot link information
107 of FIG. 2, is transmitted to the backup server 7 via e.g. an
interface 71 so as to be stored on e.g. the tapes 8.
[0205] In restoration, the backup images from the tapes 8 are
restored from the backup server 7, without the intermediary of the
switch 100, to the two file servers 3 (NAS devices).
[0206] The pseudo file system information (PFS information), backed
up e.g. on the tapes 8, is transmitted from the backup server 7 via
e.g. the interface 71 to the switch 100, for restoration.
[0207] A virtual file system, at the time of the snapshot
restoration, viewed via switch 100 from the client, may be
restored. When a file access request is made from the client, the
server identification information is inserted into the object ID.
Based on this server identification information, the switch 100
transmits the file access request to the destination server 3. As
at the time before backup/restore, the client is able to access the
object of the virtual file system at the time of the snapshot
generation.
[0208] The backup/restore command in the server may be transferred
from the client via switch to the server. Requests may be made by
the file server as the backup client, and, responsive to the
requests, the backup server may be connected to the file system of
the file server to take a backup. It may also be the data
management application (DMA) that issues a command in accordance
with the NDMP.
[0209] Thus, in the present embodiment, an administrator does not
have to map the plural file systems to the virtual file system, by
taking a backup image of a single virtual file system, virtually
prepared from the plural file systems, using the virtualized
snapshots, with the result that the maintenance and management may
be facilitated appreciably. That is, safety of data and system
reliability may be assured as the load in the maintenance and
management is relieved.
[0210] Although the above-described embodiments are based on the
NAS, the present invention is not limited to the NAS and may be
applied to optional file servers attached to the Internet. Although
the present invention has so far been described with reference to
certain preferred embodiments, the present invention is not limited
to the configuration of these embodiments and may encompass various
changes or corrections that may readily occur to those skilled in
the art within the scope of the invention as defined in the
claims.
[0211] It should be noted that other objects, features and aspects
of the present invention will become apparent in the entire
disclosure and that modifications may be done without departing the
gist and scope of the present invention as disclosed herein and
claimed as appended herewith.
[0212] Also it should be noted that any combination of the
disclosed and/or claimed elements, matters and/or items may fall
under the modifications aforementioned.
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