U.S. patent application number 16/671249 was filed with the patent office on 2021-05-06 for accessing secondary storage.
This patent application is currently assigned to EMC IP Holding Company LLC. The applicant listed for this patent is EMC IP Holding Company LLC. Invention is credited to Douglas E. LeCrone, Bruce A. Pocock.
Application Number | 20210133132 16/671249 |
Document ID | / |
Family ID | 1000005535248 |
Filed Date | 2021-05-06 |
![](/patent/app/20210133132/US20210133132A1-20210506\US20210133132A1-2021050)
United States Patent
Application |
20210133132 |
Kind Code |
A1 |
LeCrone; Douglas E. ; et
al. |
May 6, 2021 |
ACCESSING SECONDARY STORAGE
Abstract
A host coupled to a storage system accesses secondary storage
coupled to the storage system and to the host by determining if
direct data access between the storage system and the secondary
storage is operational, the host forwarding commands to the storage
system to directly access the secondary storage in response to
direct data access between the storage system and the secondary
storage being operational, and the host generating modified
commands to cause the host to directly access the secondary storage
in response to direct data access between the storage system and
the secondary storage not being operational. The secondary storage
may be a cloud storage. The secondary storage may be a tape
emulation unit. The host may directly access data of the tape
emulation unit by accessing a storage device of the tape emulation
unit. Commands on the host may be modified by a drivers layer on
the host.
Inventors: |
LeCrone; Douglas E.;
(Hopkinton, MA) ; Pocock; Bruce A.; (Hoschton,
GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EMC IP Holding Company LLC |
Hopkinton |
MA |
US |
|
|
Assignee: |
EMC IP Holding Company LLC
Hopkinton
MA
|
Family ID: |
1000005535248 |
Appl. No.: |
16/671249 |
Filed: |
November 1, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F 13/28 20130101;
G06F 13/102 20130101; G06F 13/105 20130101 |
International
Class: |
G06F 13/28 20060101
G06F013/28; G06F 13/10 20060101 G06F013/10 |
Claims
1. A method for a host coupled to a storage system to access
secondary storage coupled to the storage system and to the host,
comprising: determining if direct data access between the storage
system and the secondary storage is operational, wherein the
storage system provides non-volatile storage of data; the host
forwarding commands to the storage system to directly access the
secondary storage in response to direct data access between the
storage system and the secondary storage being operational; and the
host generating modified commands to cause the host to directly
access the secondary storage in response to direct data access
between the storage system and the secondary storage not being
operational.
2. A method, according to claim 1, wherein the secondary storage is
a cloud storage.
3. A method, according to claim 1, wherein the secondary storage is
a tape emulation unit.
4. A method, according to claim 3, wherein the host directly
accesses data of the tape emulation unit by accessing a storage
device of the tape emulation unit.
5. A method, according to claim 1, wherein the host only modifies
commands that would have caused direct data access between the
storage system and the secondary storage.
6. A method, according to claim 1, wherein commands on the host are
modified by a drivers layer on the host.
7. A method, according to claim 1, wherein the host accesses data
on the storage system following directly accessing data on the
secondary storage.
8. A non-transitory computer readable medium containing software
that causes a host coupled to a storage system to access secondary
storage coupled to the storage system and to the host, comprising:
executable code that determines if direct data access between the
storage system and the secondary storage is operational, wherein
the storage system provides non-volatile storage of data;
executable code that causes the host to forward commands to the
storage system to directly access the secondary storage in response
to direct data access between the storage system and the secondary
storage being operational; and executable code that causes the host
to generate modified commands to cause the host to directly access
the secondary storage in response to direct data access between the
storage system and the secondary storage not being operational.
9. A non-transitory computer readable medium, according to claim 8,
wherein the secondary storage is a cloud storage.
10. A non-transitory computer readable medium, according to claim
8, wherein the secondary storage is a tape emulation unit.
11. A non-transitory computer readable medium, according to claim
10, wherein the host directly accesses data of the tape emulation
unit by accessing a storage device of the tape emulation unit.
12. A non-transitory computer readable medium, according to claim
8, wherein the host only modifies commands that would have caused
direct data access between the storage system and the secondary
storage.
13. A non-transitory computer readable medium, according to claim
8, wherein commands on the host are modified by a drivers layer on
the host.
14. A method, according to claim 8, wherein the host accesses data
on the storage system following directly accessing data on the
secondary storage.
15. A system, comprising: a storage system; a secondary storage
coupled to the storage system; and a host, coupled to the storage
system and the secondary storage system, the host including a
processor that executes software on a non-transitory computer
readable medium, the software including executable code that
determines if direct data access between the storage system and the
secondary storage is operational, wherein the storage system
provides non-volatile storage of data, executable code that causes
the host to forward commands to the storage system to directly
access the secondary storage in response to direct data access
between the storage system and the secondary storage being
operational, and executable code that causes the host to generate
modified commands to cause the host to directly access the
secondary storage in response to direct data access between the
storage system and the secondary storage not being operational.
16. A system, according to claim 15, wherein the secondary storage
is a cloud storage.
17. A system, according to claim 15, wherein the secondary storage
is a tape emulation unit.
18. A system, according to claim 17, wherein the host directly
accesses data of the tape emulation unit by accessing a storage
device of the tape emulation unit.
19. A system, according to claim 15, wherein the host only modifies
commands that would have caused direct data access between the
storage system and the secondary storage.
20. A system, according to claim 15, wherein the host accesses data
on the storage system following directly accessing data on the
secondary storage.
Description
TECHNICAL FIELD
[0001] This application relates to the field of computer systems
and storage systems therefor and, more particularly, to the field
of transferring data between storage systems.
BACKGROUND OF THE INVENTION
[0002] Host processor systems (hosts) may store and retrieve data
using a storage system containing a plurality of host interface
units (I/O modules), physical storage units (e.g., disk drives,
solid state drives), and disk interface units (disk adapters). The
host systems access the storage system through a plurality of
channels provided therewith. Host systems provide data and access
control information through the channels to the storage system and
the storage system provides data to the host systems also through
the channels. The host systems do not address the physical storage
units of the storage system directly, but rather, access what
appears to the host systems as a plurality of logical volumes. The
logical volumes may or may not correspond to the physical storage
units. Allowing multiple host systems to access the single storage
system allows the host systems to share data stored therein.
[0003] In some cases, it is desirable to use secondary storage that
is coupled to a storage system for data transfers directly between
the storage system and the secondary storage. The secondary storage
may be cloud storage, a tape device (e.g., a tape emulation
device), or some other type of secondary storage. Data may be
transferred directly between the storage system and the secondary
storage based on commands and data from applications running on a
host. For example, an application running on a host may instruct
the storage system to transfer particular data from the storage
system to a tape emulation device. Transferring data directly
between the storage system and the secondary storage reduces any
inefficiencies that would occur if the data were being transferred
via the host.
[0004] However, in some cases, it may not be possible to transfer
data directly between a storage system and secondary storage. For
example, a storage system may not be configurable for directly
accessing cloud storage and/or a tape unit. Moreover, even in
instances where a storage system may be configurable to access
secondary storage, there may be policy/security reasons to prevent
direct access nonetheless. In addition, storage systems that are
configured for direct access to secondary storage may have that
access interrupted by, for example, hardware or communication
failures during operation. Applications on the host that expect
direct access between the storage system and the secondary storage
either need to be rewritten when direct access is not available or
need to contain logic to anticipate that access may or may not be
available. Rewriting applications may not be practical, especially
for legacy applications for which source code may not be
available.
[0005] Accordingly, it is desirable to provide a mechanism to allow
access to secondary storage in systems where direct access between
a storage system and secondary storage is not necessarily
available.
SUMMARY OF THE INVENTION
[0006] According to the system described herein, a host coupled to
a storage system accesses secondary storage coupled to the storage
system and to the host by determining if direct data access between
the storage system and the secondary storage is operational, the
host forwarding commands to the storage system to directly access
the secondary storage in response to direct data access between the
storage system and the secondary storage being operational, and the
host generating modified commands to cause the host to directly
access the secondary storage in response to direct data access
between the storage system and the secondary storage not being
operational. The secondary storage may be a cloud storage. The
secondary storage may be a tape emulation unit. The host may
directly access data of the tape emulation unit by accessing a
storage device of the tape emulation unit. The host may only
modifies commands that would have caused direct data access between
the storage system and the secondary storage. Commands on the host
may be modified by a drivers layer on the host. The host may access
data on the storage system following directly accessing data on the
secondary storage.
[0007] According further to the system described herein, a
non-transitory computer readable medium contains software that
causes a host coupled to a storage system to access secondary
storage coupled to the storage system and to the host. The software
includes executable code that determines if direct data access
between the storage system and the secondary storage is
operational, executable code that causes the host to forward
commands to the storage system to directly access the secondary
storage in response to direct data access between the storage
system and the secondary storage being operational, and executable
code that causes the host to generate modified commands to cause
the host to directly access the secondary storage in response to
direct data access between the storage system and the secondary
storage not being operational. The secondary storage may be a cloud
storage. The secondary storage may be a tape emulation unit. The
host may directly access data of the tape emulation unit by
accessing a storage device of the tape emulation unit. The host may
only modifies commands that would have caused direct data access
between the storage system and the secondary storage. Commands on
the host may be modified by a drivers layer on the host. The host
may access data on the storage system following directly accessing
data on the secondary storage.
[0008] According further to the system described herein, a system
includes a storage system, a secondary storage coupled to the
storage system, and a host, coupled to the storage system and the
secondary storage system. The host includes a processor that
executes software on a non-transitory computer readable medium, the
software including executable code that determines if direct data
access between the storage system and the secondary storage is
operational, executable code that causes the host to forward
commands to the storage system to directly access the secondary
storage in response to direct data access between the storage
system and the secondary storage being operational, and executable
code that causes the host to generate modified commands to cause
the host to directly access the secondary storage in response to
direct data access between the storage system and the secondary
storage not being operational. The secondary storage may be a cloud
storage. The secondary storage may be a tape emulation unit. The
host may directly access data of the tape emulation unit by
accessing a storage device of the tape emulation unit. The host may
only modifies commands that would have caused direct data access
between the storage system and the secondary storage. Commands on
the host may be modified by a drivers layer on the host. The host
may access data on the storage system following directly accessing
data on the secondary storage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments of the system are described with reference to
the several figures of the drawings, noted as follows.
[0010] FIG. 1 is a schematic illustration showing a relationship
between a host and a storage system that may be used in connection
with an embodiment of the system described herein.
[0011] FIG. 2 is a schematic diagram illustrating an embodiment of
a storage system where each of a plurality of directors are coupled
to a memory according to an embodiment of the system described
herein.
[0012] FIGS. 3A and 3B are schematic diagrams showing a cloud
storage and storage systems coupled thereto according to
embodiments of the system described herein.
[0013] FIG. 4 is a schematic diagram showing a host, a storage
system, and a tape emulation device used in connection with an
embodiment of the system described herein.
[0014] FIG. 5 is a schematic diagram illustrating a tape emulation
device according to an embodiment of the system described
herein.
[0015] FIG. 6 is a schematic illustration showing a system with a
FICON connection between a host and a data storage system according
to an embodiment of the system described herein.
[0016] FIG. 7 is a schematic illustration showing software layers
in a host according to an embodiment of the system described
herein.
[0017] FIG. 8 is a flow diagram illustrating providing access to
secondary storage according to an embodiment of the system
described herein.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0018] The system described herein provides access to secondary
storage by a host in systems where direct access between a storage
system and secondary storage is not necessarily available. A
drivers layer of the host intercepts and modifies commands/data
that are meant to instruct the storage device to directly access
secondary storage. The modifications cause the host, instead of the
storage system, to access the secondary storage.
[0019] FIG. 1 is a diagram 20 showing a relationship between a host
22 and a storage system 24 that may be used in connection with an
embodiment of the system described herein. In an embodiment, the
storage system 24 may be a Symmetrix, PowerMax or VMAX storage
system produced by Dell EMC of Hopkinton, Mass.; however, the
system described herein may operate with other appropriate types of
storage systems. Also illustrated is another (remote) storage
system 26 that may be similar to, or different from, the storage
system 24 and may, in various embodiments, be coupled to the
storage system 24, using, for example, a network. The host 22 reads
and writes data from and to the storage system 24 via an HA 28
(host adapter), which facilitates an interface between the host 22
and the storage system 24. Although the diagram 20 shows the host
22 and the HA 28, it will be appreciated by one of ordinary skill
in the art that multiple host adaptors (possibly of different
configurations) may be used and that one or more HAs may have one
or more hosts coupled thereto.
[0020] In an embodiment of the system described herein, in various
operations and scenarios, data from the storage system 24 may be
copied to the remote storage system 26 via a link 29. For example,
transferring data may be part of a data mirroring or replication
process that causes data on the remote storage system 26 to be
identical to the data on the storage system 24. Although only the
one link 29 is shown, it is possible to have additional links
between the storage systems 24, 26 and to have links between one or
both of the storage systems 24, 26 and other storage systems (not
shown). The storage system 24 may include a first plurality of
remote adapter units (RA's) 30a, 30b, 30c. The RA's 30a-30c may be
coupled to the link 29 and be similar to the HA 28, but are used to
transfer data between the storage systems 24, 26.
[0021] The storage system 24 may include one or more physical
storage units (including disks, solid state storage devices, etc.),
each containing a different portion of data stored on the storage
system 24. FIG. 1 shows the storage system 24 having a plurality of
physical storage units 33a-33c. The storage system 24 (and/or
remote storage system 26) may be provided as a stand-alone device
coupled to the host 22 as shown in FIG. 1 or, alternatively, the
storage system 24 (and/or remote storage system 26) may be part of
a storage area network (SAN) that includes a plurality of other
storage systems as well as routers, network connections, etc. (not
shown in FIG. 1). The storage systems may be coupled to a SAN
fabric and/or be part of a SAN fabric. The system described herein
may be implemented using software, hardware, and/or a combination
of software and hardware where software may be stored in a computer
readable medium and executed by one or more processors.
[0022] Each of the physical storage units 33a-33c may be coupled to
a corresponding disk adapter unit (DA) 35a-35c that provides data
to a corresponding one of the physical storage units 33a-33c and
receives data from a corresponding one of the physical storage
units 33a-33c. An internal data path exists between the DA's
35a-35c, the HA 28 and the RA's 30a-30c of the storage system 24.
Note that, in other embodiments, it is possible for more than one
physical storage unit to be serviced by a DA and that it is
possible for more than one DA to service a physical storage unit.
The storage system 24 may also include a global memory 37 that may
be used to facilitate data transferred between the DA's 35a-35c,
the HA 28 and the RA's 30a-30c as well as facilitate other
operations. The memory 37 may contain task indicators that indicate
tasks to be performed by one or more of the DA's 35a-35c, the HA 28
and/or the RA's 30a-30c, and may contain a cache for data fetched
from one or more of the physical storage units 33a-33c.
[0023] The storage space in the storage system 24 that corresponds
to the physical storage units 33a-33c may be subdivided into a
plurality of volumes or logical devices. The logical devices may or
may not correspond to the storage space of the physical storage
units 33a-33c. Thus, for example, the physical storage unit 33a may
contain a plurality of logical devices or, alternatively, a single
logical device could span both of the physical storage units 33a,
33b. Similarly, the storage space for the remote storage system 26
may be subdivided into a plurality of volumes or logical devices,
where each of the logical devices may or may not correspond to one
or more physical storage units of the remote storage system 26.
[0024] In some embodiments, an other host 22' may be provided. The
other host 22' is coupled to the remote storage system 26 and may
be used for disaster recovery so that, upon failure at a site
containing the host 22 and the storage system 24, operation may
resume at a remote site containing the remote storage system 26 and
the other host 22'. In some cases, the host 22 may be directly
coupled to the remote storage system 26, thus protecting from
failure of the storage system 24 without necessarily protecting
from failure of the host 22.
[0025] FIG. 2 is a schematic diagram 40 illustrating an embodiment
of the storage system 24 where each of a plurality of directors
42a-42n are coupled to the memory 37. Each of the directors 42a-42n
represents at least one of the HA 28, RAs 30a-30c, or DAs 35a-35c.
The diagram 40 also shows an optional communication module (CM) 44
that provides an alternative communication path between the
directors 42a-42n. Each of the directors 42a-42n may be coupled to
the CM 44 so that any one of the directors 42a-42n may send a
message and/or data to any other one of the directors 42a-42n
without needing to go through the memory 37. The CM 44 may be
implemented using conventional MUX/router technology where one of
the directors 42a-42n that is sending data provides an appropriate
address to cause a message and/or data to be received by an
intended one of the directors 42a-42n that is receiving the data.
Some or all of the functionality of the CM 44 may be implemented
using one or more of the directors 42a-42n so that, for example,
the directors 42a-42n may be interconnected directly with the
interconnection functionality being provided on each of the
directors 42a-42n. In addition, one or more of the directors
42a-42n may be able to broadcast a message to all or at least some
plurality of the other directors 42a-42n at the same time.
[0026] In some embodiments, one or more of the directors 42a-42n
may have multiple processor systems thereon and thus may be able to
perform functions for multiple discrete directors. In some
embodiments, at least one of the directors 42a-42n having multiple
processor systems thereon may simultaneously perform the functions
of at least two different types of directors (e.g., an HA and a
DA). Furthermore, in some embodiments, at least one of the
directors 42a-42n having multiple processor systems thereon may
simultaneously perform the functions of at least one type of
director and perform other processing with the other processing
system. In addition, all or at least part of the global memory 37
may be provided on one or more of the directors 42a-42n and shared
with other ones of the directors 42a-42n. In an embodiment, the
features discussed in connection with the storage system 24 may be
provided as one or more director boards having CPUs, memory (e.g.,
DRAM, etc.) and interfaces with Input/Output (I/O) modules.
[0027] Note that, although specific storage system configurations
are disclosed in connection with FIGS. 1 and 2, it should be
understood that the system described herein may be implemented on
any appropriate platform. Thus, the system described herein may be
implemented using a platform like that described in connection with
FIGS. 1 and 2 or may be implemented using a platform that is
somewhat or even completely different from any particular platform
described herein.
[0028] A storage area network (SAN) may be used to couple one or
more host systems with one or more storage systems in a manner that
allows reconfiguring connections without having to physically
disconnect and reconnect cables from and to ports of the devices. A
storage area network may be implemented using one or more switches
to which the storage systems and the host systems are coupled. The
switches may be programmed to allow connections between specific
ports of devices coupled to the switches. A port that can initiate
a data-path connection may be called an "initiator" port while the
other port may be deemed a "target" port.
[0029] Referring to FIG. 3A, a diagram 300 illustrates using a
cloud storage 302. The cloud storage 302 may be a private cloud
storage provided by an organization for its own internal use, a
semi-private cloud storage provided by a collection of
organizations for use by members, or a public cloud storage such as
Amazon Web Service (AWS) or Microsoft Azure. The cloud storage 302
provides security controls so that only authorized users may access
data and possibly so that some of the users are only able to read
data. In an embodiment herein, the cloud storage 302 may be
accessible from any location via the World Wide Web, although it
may be possible to impose restrictions on access, such as
geographic restrictions (e.g., prohibiting access from Internet
addresses originating in certain countries). In other embodiments,
the cloud storage 302 may be part of a private network that is not
generally accessible, but may nonetheless be geographically
diverse.
[0030] A first storage system 304 and a second storage system 306
are couple to the cloud storage 302 and exchange data therewith.
The cloud storage acts as a secondary storage for the storage
systems 304, 306. One or both of the storage systems 304, 306 may
be similar to the storage system 24, described above, and may be
storage arrays provided by Dell EMC of Hopkinton, Mass., although
other types of storage systems are possible. Data connections
between the storage systems 304, 306 and the cloud storage 302 may
be provided by any appropriate mechanism, including the Internet,
other TCP/IP networks, dedicated connections, FICON connections,
etc. Each of the storage systems 304, 306 may provide data storage
for one or more host systems coupled thereto so that, for example,
the storage system 304 provides data storage for a host 308 and the
storage system 306 provides data storage for a host 312. The host
308 may be coupled to the storage system 304 using any appropriate
mechanism. Similarly, the host 312 may be coupled to the storage
system 308 using any appropriate mechanism. Data is exchanged
between the cloud storage 302 and the storage system 304.
Similarly, data is exchanged between the cloud storage 302 and the
storage system 306. The hosts 308, 312 may be coupled directly to
the cloud storage 302 (shown in FIG. 3A as dashed lines) to provide
an alternative data transfer mechanism between the hosts 308, 312
and the cloud storage 302, described in more detail elsewhere
herein.
[0031] Referring to FIG. 3B, a diagram 300' illustrates a system
that is similar to the system described above in connection with
the diagram 300. The diagram 300' shows the storage systems 304,
306 coupled to the cloud storage 302, which acts as a secondary
storage. However, in the diagram 300', a host 314 is coupled to
both the storage system 304 and the storage system 306. Data is
exchanged between the cloud storage 302 and the storage system 304
and exchanged between the cloud storage 302 and the storage system
306. The host 314 may be coupled directly to the cloud storage 302
(shown in FIG. 3B as a dashed line) to provide an alternative data
transfer mechanism between the host 314 and the cloud storage 302,
described in more detail elsewhere herein.
[0032] Referring to FIG. 4, a diagram 400 shows a host 402 coupled
to a storage system 404 that is coupled to a tape unit 406. The
tape unit 406 acts as a secondary storage to the storage system
404. The host 402 may be similar to the hosts 22, 22' described
above and may be any appropriate computing system, such as an IBM
System z computing system. The storage system 404 may be similar to
the storage systems 24, 26 described above and may be any storage
system capable of providing the functionality described herein,
such as a storage array provided by Dell EMC of Hopkinton, Mass.
The tape unit 406 may be any physical tape unit or may be a tape
emulation unit that provides tape emulation functionality so that a
device writes tape data and commands to the tape emulation unit 406
and reads tape data and status information from the tape emulation
unit 406 as if the tape emulation unit 406 were an actual computer
tape device. The tape unit 406 may be implemented using any
appropriate device, such as the DLm960 tape emulation device
provided by Dell EMC of Hopkinton, Mass. The tape unit 406 may also
correspond to any out-of-band (00B) storage mechanism that
represents additional storage capability beyond storage
capabilities provided by the storage system 404. In an embodiment
herein, data is exchanged with the tape unit 406 using any
appropriate format. Note that, although only a single host 402, a
single storage system 404, and a single tape unit 406 are shown, it
is understood by one of ordinary skill in the art that the system
may be extended to have more than one of one or more of each.
[0033] The host 402, the storage system 404, and the tape unit 406
may be coupled using a conventional FICON connection or possibly a
network, such as the Internet, a different TCP/IP network, a SAN, a
WAN, and/or any other appropriate mechanism for transporting data
between the host 402 and the storage system 404 and between the
storage system 404 and the tape unit 406. Data connections between
the components may be synchronous or asynchronous (or possibly a
combination thereof). The host 402 may be coupled directly to the
tape unit 406 (shown in FIG. 4 as a dashed line) to provide an
alternative data transfer mechanism between the host 402 and the
tape unit 406, described in more detail elsewhere herein.
[0034] Referring to FIG. 5, the tape unit 406 is shown in more
detail as a tape emulation unit that includes a front end component
502, a data mover/server 504, and a tape emulation storage device
506 coupled thereto. The front end component 502 may include a
FICON link that may be coupled to the storage system 404 for data
communication between the storage system 404 and the tape unit 406.
Other types of links may be used. The front end component 502 may
include FICON link emulation functionality as well as tape
emulation functionality, such as that provided by components of the
DLm960.
[0035] The data mover/server 504 may be coupled to the front end
component 502 using, for example, a GigE switch while the storage
device 506 is coupled to the data mover/server 504 using any
appropriate protocol, such as Fibre Channel. The data mover/server
504 may be accessed by the front end component 502 using any
appropriate protocol, such as NFS (Network File System). In an
embodiment herein, the data mover/server 504 may include an NFS
server, such as a Celerra data mover, and the storage device 506
may be a Clarrion or Symmetrix data storage array. There may be
other components used instead of, and/or in addition to, the NFS
server and the data storage array.
[0036] In the system described herein, the storage device 404 is
coupled directly to the tape unit 406. The storage device 404 is
configured to act as a host with respect to the connection between
the storage device 404 and the tape unit 406. In an embodiment
herein, the storage device 404 and the tape unit 406 are coupled
using a conventional FICON channel/protocol so that the storage
device 404 acts as a FICON initiator to the tape unit 406. If the
FICON channel at the storage device 404 supports the IBM 3590
protocol, then the tape unit 406 could be a Dell/EMC DLm960 virtual
tape unit. Of course, any other type of tape unit may be used,
including an actual tape drive and it is also possible to use any
type of out-of-band (00B) storage.
[0037] In the system described herein, the host 402 sends metadata
information to the storage device 404 to direct the storage device
404 to exchange data with the tape unit 406. Thus, relatively large
amounts of data may exchanged between the storage device 404 and
the tape unit 406 without transferring any data through the host
402. Moreover, unlike solutions described in U.S. Pat. No.
9,645,766 titled "TAPE EMULATION ALTERNATE DATA PATH" to Douglas E.
LeCrone, which is incorporated by reference herein, the system
described herein does not require that the tape unit 406 be
modified from an off-the-shelf configuration since the storage
device 404 emulates a host when coupled to the tape unit 406. In an
embodiment herein, the host 402 provides metadata to the storage
device 404 using any appropriate format that can be detected and
interpreted by the storage device 404.
[0038] FIG. 6 is a schematic illustration showing a host 602 with a
FICON connection controller 604 for providing a FICON connection
between the host 602 and a data storage system 606 according to an
embodiment of the system described herein. The host 602 is similar
to the hosts 22, 22' discussed above and may be a computer running
Linux or some other appropriate operating system 608. The data
storage system 606 is similar to the data storage systems 24, 26
discussed elsewhere herein. I/O processing on the host 602 may
operate with the FICON connection controller 604 to enable I/O
operations with the data storage system 606. The FICON connection
controller 604 may send and receive data to and from the data
storage system 606 using a remote connection mechanism 612 that may
include a network (such as the Internet, and appropriate connection
thereof). The data storage system 606 may include physical storage
volumes and/or logical volumes, such as Dell EMC's data storage
facility. The FICON connection controller 604 may act as an I/O
subsystem providing FICON communication capability. The data
storage system 606 may include features and/or components enabling
FICON channel communication with the host 602. For a discussion of
features and implementations of FICON systems and suitable channel
protocols operating therewith on z/Architecture computing systems,
reference is made to J. Entwistle, "IBM System z10 FICON Express8
FCP Channel Performance Report," Technical paper, August 2009, 27
pp., which is incorporated herein by reference.
[0039] It is noted that various components of the system may be
emulated. For further discussion of emulation of I/O computing
components, particular Fibre Channel/FICON connection components,
reference is made to U.S. Pat. No. 9,665,502 to Jones et al.,
issued May 30, 2017, entitled "Virtual I/O Hardware" and to U.S.
Pat. No. 9,170,904 to LeCrone et al., issued Oct. 27, 2015,
entitled "I/O Fault Injection Using Simulated Computing
Environments," which are both incorporated herein by reference.
Accordingly, in various embodiments, the system described herein
provides for use of a channel emulator to emulate data transfer
paths in I/O operations, and in which the channel emulator may
simulate a host channel to provide I/O connectivity with an I/O
device and may provide for the I/O connectivity using different
channel protocols.
[0040] The connection mechanism 612 may include an Internet
connection and/or possibly some other types of connection(s). In an
embodiment herein, the connection mechanism 612 may be directly
incompatible with a FICON connection. The incompatibility may be
hardware incompatibility, software incompatibility, or both. The
connection mechanism 612 may not support a direct FICON connection
but, instead, rely on a FICON emulator (and/or other emulator(s))
for providing data in an appropriate format. It is further noted
that where FICON emulation is being performed, the data storage
system 606 may include or be coupled to a FICON emulator portion
that may send and receive data to and from the connection mechanism
612 and also emulates a Fibre Channel FCO physical layer for the
benefit of the data storage system 606. Thus, in such a case
involving emulation, both the host 602 and the data storage system
606 may operate as if the devices 602, 606 were communicating using
a FICON hardware connection.
[0041] In an embodiment, the system described herein may be used
with IBM's z High Performance FICON (zHPF) transport mode protocol
implementation. zHPF enhances z/Architecture and FICON interface
architecture to improve data transfer processing. In z/OS, standard
FICON architecture operates with the command mode protocol, and a
zHPF architecture operates with the transport mode protocol. zHPF
provides a Transport Control Word (TCW) that facilitates the
processing of an I/O request by the channel and the controller. The
TCW enables multiple channel commands to be sent to the controller
as a single entity (instead of being sent as separate commands as
in a FICON channel command word (CCW)). The channel no longer has
to process and keep track of each individual CCW. The channel
forwards a chain of commands to the controller for execution. zHPF
capable channels may support both FICON and zHPF protocols
simultaneously. For a more detailed discussion of zHPF, reference
is made, for example, to C. Cronin, "IBM System z10 I/O and High
Performance FICON for System z Channel Performance," Technical
paper, IBM Corporation, Jan. 28, 2009, 33 pp., which is
incorporated herein by reference.
[0042] Referring to FIG. 7, the host 602 is illustrated with
software 700 having an application(s) layer 702, an access methods
layer 704, a drivers layer 706, and a channel subsystem layer 708.
The application(s) layer 702 includes one or more software
applications that run on the host 602. The access methods layer 704
includes I/O routines (e.g., read, write, open, etc.) that are used
by applications in the application(s) layer 702 in connection with
performing I/O operations. Software in the application(s) layer 702
calls specific routines in the access methods layer 704 to access
data on a storage device coupled to the host.
[0043] The I/O routines in the access methods layer 704 call driver
routines in the drivers layer 706 that perform lower-level device
specific operations that depend upon the specific type of I/O
device and the type of connection thereto. For example, a first
driver for a Symmetrix storage device coupled to the host 602 by a
FICON connection may be different than a second driver used for a
different type of non-volatile storage device coupled to the host
602 using a different type of connection. Note, however, that an
application in the application layer 702 may call the same routine
(e.g., read) in the access layer 704 irrespective of the physical
hardware (and connection there) used for the data, but that the
routine in the access layer 704 that is called may call different
routines in the drivers layer 706, depending upon a specific
configuration/hardware of the system.
[0044] The channel subsystem layer 708 includes routines that
control the hardware used for I/O operations, including any storage
devices and channels used for transferring data between the host
602 and the storage system 606. Routines in the drivers layer 706
call routines in the channel subsystem layer 708 to perform
hardware operations and to transfer data to and from the host 602
and to exchange status and control information to facilitate
control of the I/O hardware. In an embodiment herein, special
routines are provided in the drivers layer 706 that provide
alternative processing for commands to the data storage system 606
that cause the data storage device to directly access either the
cloud storage 302 (described above in connection with FIG. 3A and
FIG. 3B) or directly access the tape unit 406 (described above in
connection with FIG. 5).
[0045] Referring to FIG. 8, a flow diagram 800 illustrates
processing performed by the drivers layer 706 in connection with
processing commands and data being transmitted from the host 602 to
the data storage system 606. The system describes herein provides
an alternative data path from the host 602 to secondary storage
(e.g., cloud storage or a tape unit) in response to detecting that
an expected data connection between the storage system 606 and
cloud storage (like the cloud storage 302, discussed above) or an
expected connection between the storage system 606 and a tape unit
(like the tape unit 406, discussed above) is not available. Note
that an expected data connection from the storage device 606 to
secondary storage may not be available for any number of reasons,
including a hardware failure, a communication failure, or in cases
where the storage system 606 does not have the capability to
communicate with cloud storage and/or a tape unit either because
the storage system 606 has never been properly configured or
because necessary hardware or software capabilities are not
present. In such a case, the host 602 may take over and perform the
transfers to the secondary storage that would otherwise be
performed by the storage system 606. The takeover may occur
automatically without the need to modify any applications running
on the host 602 because of the use of special routines in the
drivers layer 706.
[0046] Processing for the flow diagram 800 begins at a test step
802 where it is determined if expected data transfers between the
storage system 606 and secondary storage are operational/available.
The test at the step may be performed by examining status and
capability information for the storage system 606 or may be
configured manually by an operator (e.g., an operator manually
indicates whether the storage system 606 is capable of directly
transferring data to a cloud storage and/or a tape unit) or by some
other appropriate mechanism. If it is determined at a test step 802
that the expected direct data transfers between the storage system
606 and secondary storage (cloud storage and/or a tape unit) are
operational/available, then control transfers from the test step
802 to a step 804 where the drivers layer 706 passes through the
command/data to the storage system 606 without any changes. For
example, the command/data may instruct the storage system 606 to
directly transfer specific data to a particular cloud storage. If
the storage system/secondary storage mechanism is operational, the
command/data to instruct the storage system 606 to directly
transfer specific data to a particular cloud storage is passed
through at the step 804. Of course, it is possible that the
command/data passed through at the step 804 is not related to
transferring data between the storage system 606 and secondary
storage. Generally, commands and data from the host 602 to the
storage system 606 are transmitted at the step 804 without any
modification. Following the step 804, control transfers back to the
step 802, discussed above, for another iteration.
[0047] If it is determined at a test step 802 that expected direct
data transfers between the storage device 606 and secondary storage
(cloud storage and/or a tape unit) are not operational, then
control transfers from the test step 802 to a test step 806 where
it is determined if the command/data being processed relates to
transferring data from the storage system 606 to secondary storage.
If not, then control transfers from the test step 806 to the step
804, discussed above, where the drivers layer 706 passes through
the command/data to the storage system 606 with any modifications.
That is, even if transferring data directly between the storage
system 606 and secondary storage is not operational, commands and
data that are not related to such transfers are still forwarded to
the storage system 606 without any modification. The host only
modifies commands that would have caused direct data access between
the storage system 606 and the secondary storage. Following the
step 804, control transfers back to the step 802, discussed above,
for another iteration.
[0048] If it determined at the test step 806 that that the
command/data being processed relates to transferring data from the
storage system 606 to secondary storage, then control transfers
from the test step 806 to a step 808 where the command is modified
to cause the host 602 to transfer the command/data to the secondary
storage device directly in place of the storage system 606
transferring the command/data to the secondary storage system. For
example, if the secondary storage is cloud storage (like the cloud
storage 302, described above), then processing at the step 808 may
replace a command to transfer data from the cloud storage to the
storage system 606 with a command that is sent by the host 602
directly to the cloud storage to transfer data from the cloud
storage to the host 602. If the secondary storage is a tape unit
(like the tape unit 406 described above) then processing at the
step 808 may replace a command to transfer data from the tape unit
to the storage system 606 with a command that is sent by the host
602 directly to the tape unit to transfer data from the tape unit
to the host 602. Note that, in the case of a tape emulation
device/system, such as the DLm960 tape emulation device, described
above, it is also possible to provide commands that access the tape
emulation storage device 506 directly (e.g., using NFS or OCFS2
access protocol).
[0049] Following the step 808 is a test step 812 where it is
determined if the command/data that is being replaced at the step
808 requires any data to be accessed at the storage system 606.
Note that some commands, such as a status request of the secondary
storage, may not require any access to the storage system 606.
Other commands, such as a command to transfer data from a tape unit
to the storage system 606, may require access to the storage system
606 to, for example, store or retrieve data. If it is determined at
the test step 812 that access to the storage system 606 is needed,
then control transfers from the test step 812 to a step 814 where
the storage system 606 is accessed (e.g., to transfer data
thereto). Following the step 814 is a step 816 where the drivers
layer 706 provides an appropriate response to a calling routine in
an application on the host 602 that initially invoked the command.
Note that the step 816 may be reached directly from the step 814,
described above, if it is determined at the step 814 that access to
the storage system 606 is not needed. Following the step 816,
control transfers back to the step 802, described above, for
another iteration.
[0050] Various embodiments discussed herein may be combined with
each other in appropriate combinations in connection with the
system described herein. Additionally, in some instances, the order
of steps in the flow diagrams, flowcharts and/or described flow
processing may be modified, where appropriate. Further, various
aspects of the system described herein may be implemented using
software, hardware, a combination of software and hardware and/or
other computer-implemented modules or devices having the described
features and performing the described functions. The system may
further include a display and/or other computer components for
providing a suitable interface with a user and/or with other
computers.
[0051] Software implementations of the system described herein may
include executable code that is stored in a non-transitory
computer-readable medium and executed by one or more processors.
The computer-readable medium may include volatile memory and/or
non-volatile memory, and may include, for example, a computer hard
drive, ROM, RAM, flash memory, portable computer storage media such
as a CD-ROM, a DVD-ROM, an SD card, a flash drive or other drive
with, for example, a universal serial bus (USB) interface, and/or
any other appropriate tangible or non-transitory computer-readable
medium or computer memory on which executable code may be stored
and executed by a processor. The system described herein may be
used in connection with any appropriate operating system.
[0052] Other embodiments of the invention will be apparent to those
skilled in the art from a consideration of the specification or
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with
the true scope and spirit of the invention being indicated by the
following claims.
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