U.S. patent application number 16/121290 was filed with the patent office on 2018-12-27 for distributed storage network data revision control.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Andrew Baptist, Greg Dhuse, Jason K. Resch, Ilya Volvovski.
Application Number | 20180375671 16/121290 |
Document ID | / |
Family ID | 43926523 |
Filed Date | 2018-12-27 |
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United States Patent
Application |
20180375671 |
Kind Code |
A1 |
Resch; Jason K. ; et
al. |
December 27, 2018 |
DISTRIBUTED STORAGE NETWORK DATA REVISION CONTROL
Abstract
Multiple revisions of an encoded data slice are generated, with
each revision having the same slice name. Each of the data slices
represents the same original data portion, but each is encoded so
that no single data slice can be used to reconstruct the original
data portion. Appropriate revision numbers are associated with each
encoded data slice, and the encoded data slices and associated
revision numbers are transmitted for storage in selected storage
units of a distributed storage network. If write confirmations are
received from at least a write threshold number of storage units, a
commit command is transmitted so that the most recently written
data slices will be available for access. After a commit command is
issued, a current directory used to access the encoded data slices
can be sliced, encoded, and stored in the same way as the data
slices.
Inventors: |
Resch; Jason K.; (Chicago,
IL) ; Dhuse; Greg; (Chicago, IL) ; Volvovski;
Ilya; (Chicago, IL) ; Baptist; Andrew; (Mt.
Pleasant, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
43926523 |
Appl. No.: |
16/121290 |
Filed: |
September 4, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12837961 |
Jul 16, 2010 |
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16121290 |
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12080042 |
Mar 31, 2008 |
8880799 |
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12837961 |
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61256226 |
Oct 29, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 9/3247 20130101;
G06F 11/1469 20130101; H04L 67/1097 20130101; G06F 11/1076
20130101; G06F 2211/1028 20130101; H04L 12/00 20130101 |
International
Class: |
H04L 12/00 20060101
H04L012/00; G06F 11/14 20060101 G06F011/14; H04L 9/32 20060101
H04L009/32; H04L 29/08 20060101 H04L029/08 |
Claims
1. A method for execution by a computing device that includes a
computing core, the method comprising: determining a first revision
number regarding a version of a first data segment, wherein the
first data segment is encoded using an error coding dispersal
storage function to produce a first set of encoded data slices;
associating the first revision number to each encoded data slice of
the first set of encoded data slices to produce a first set of
appended encoded data slices; transmitting, by the computing device
via an output interface, write commands regarding the first set of
appended encoded data slices to storage units of a distributed
storage network (DSN), wherein the write commands include the first
set of appended encoded data slices for storage in the storage
units; receiving write confirmation messages from at least some of
the storage units; verifying the first revision number within the
write confirmation messages; when a write threshold number of write
confirmation messages have been received and the first revision
number has been verified within each of the write threshold number
of write confirmation messages, sending write commit messages to
the storage units; and storing a current directory used to access
the encoded data slices.
2. The method of claim 1, wherein storing the current directory
used to access the encoded data slices includes slicing the current
directory.
3. The method of claim 1, wherein storing the current directory
used to access the encoded data slices includes encoding the
current directory using an error coding dispersal storage
function.
4. The method of claim 1, wherein the first revision number is
appended to each encoded data slice of the first set of encoded
data slices.
5. The method of claim 1 further comprising: determining whether
write commit responses have been received from at least some of the
storage units, wherein a write commit response indicates that a
storage unit has made a corresponding encoded data slice
visible.
6. The method of claim 1 further comprising: when the write
confirmations for the at least the write threshold number of each
of the first set of appended encoded data slices have not been
received, retransmitting at least some of the write commands to
different storage units.
7. The method of claim 1, further comprising: determining the first
revision numbers based on at least one of a timestamp, a random
number, a user vault identifier, a user identifier, a data object
identifier, a hash of the first data segment, and a hash of a data
segment identifier.
8. A distributed storage computing device comprising: an interface;
memory; and a processing system, including a processor and operably
coupled to the interface and to the memory, wherein the processing
system is operable to perform operations including: determining a
first revision number regarding a version of a first data segment,
wherein the first data segment is encoded using an error coding
dispersal storage function to produce a first set of encoded data
slices; associating the first revision number to each encoded data
slice of the first set of encoded data slices to produce a first
set of appended encoded data slices; transmitting, via an output
interface, write commands regarding the first set of appended
encoded data slices to storage units of a distributed storage
network (DSN), wherein the write commands include the first set of
appended encoded data slices for storage in the storage units;
receiving write confirmation messages from at least some of the
storage units; verifying the first revision number within the write
confirmation messages; when a write threshold number of write
confirmation messages have been received and the first revision
number has been verified within each of the write threshold number
of write confirmation messages, sending write commit messages to
the storage units; and storing a current directory used to access
the encoded data slices.
9. The distributed storage computing device of claim 8, wherein
storing the current directory used to access the encoded data
slices includes slicing the current directory.
10. The distributed storage computing device of claim 8, wherein
storing the current directory used to access the encoded data
slices includes encoding the current directory using an error
coding dispersal storage function.
11. The distributed storage computing device of claim 8, wherein
the first revision number is appended to each encoded data slice of
the first set of encoded data slices.
12. The distributed storage computing device of claim 8, wherein
the operations further include: determining whether write commit
responses have been received from at least some of the storage
units, wherein a write commit response indicates that a storage
unit has made a corresponding encoded data slice visible.
13. The distributed storage computing device of claim 8, wherein
the operations further include: when the write confirmations for
the at least the write threshold number of each of the first set of
appended encoded data slices have not been received, retransmitting
at least some of the write commands to different storage units.
14. The distributed storage computing device of claim 8, wherein
the operations further include: determining the first revision
numbers based on at least one of a timestamp, a random number, a
user vault identifier, a user identifier, a data object identifier,
a hash of the first data segment, and a hash of a data segment
identifier.
15. A computer readable storage medium comprises: at least one
memory section that stores operational instructions that, when
executed by a processing system of a dispersed storage and task
(DST) execution unit that includes a hardware processor and a
memory, causes the processing system to perform operations
including: determining a first revision number regarding a version
of a first data segment, wherein the first data segment is encoded
using an error coding dispersal storage function to produce a first
set of encoded data slices; associating the first revision number
to each encoded data slice of the first set of encoded data slices
to produce a first set of appended encoded data slices;
transmitting, via an output interface, write commands regarding the
first set of appended encoded data slices to storage units of a
distributed storage network (DSN), wherein the write commands
include the first set of appended encoded data slices for storage
in the storage units; receiving write confirmation messages from at
least some of the storage units; verifying the first revision
number within the write confirmation messages; when a write
threshold number of write confirmation messages have been received
and the first revision number has been verified within each of the
write threshold number of write confirmation messages, sending
write commit messages to the storage units; and storing a current
directory used to access the encoded data slices.
16. The computer readable storage medium of claim 15, wherein
storing the current directory used to access the encoded data
slices includes slicing the current directory.
17. The computer readable storage medium of claim 15, wherein
storing the current directory used to access the encoded data
slices includes encoding the current directory using an error
coding dispersal storage function.
18. The computer readable storage medium of claim 15, wherein the
first revision number is appended to each encoded data slice of the
first set of encoded data slices.
19. The computer readable storage medium of claim 15, wherein the
operations further include: determining whether write commit
responses have been received from at least some of the storage
units, wherein a write commit response indicates that a storage
unit has made a corresponding encoded data slice visible.
20. The computer readable storage medium of claim 15, wherein the
operations further include: when the write confirmations for the at
least the write threshold number of each of the first set of
appended encoded data slices have not been received, retransmitting
at least some of the write commands to different storage units.
Description
CROSS REFERENCE TO RELATED PATENTS
[0001] The present U.S. Utility Patent Application claims priority
pursuant to 35 U.S.C. .sctn. 120 as a continuation of U.S. Utility
application Ser. No. 12/837,961, entitled "DISTRIBUTED STORAGE
NETWORK DATA REVISION CONTROL", filed Jul. 16, 2010, which claims
priority pursuant to 35 U.S.C. .sctn. 119(e) to U.S. Provisional
Application No. 61/256,226, entitled "DISTRIBUTED STORAGE NETWORK
DATA REVISION CONTROL", filed Oct. 29, 2009, both of which are
hereby incorporated herein by reference in their entirety and made
part of the present U.S. Utility Patent Application for all
purposes.
[0002] U.S. Utility application Ser. No. 12/837,961 also claims
priority pursuant to 35 U.S.C. .sctn. 120 as a continuation-in-part
of U.S. Utility application Ser. No. 12/080,042, entitled
"REBUILDING DATA ON A DISPERSED STORAGE NETWORK", filed Mar. 31,
2008, issued as U.S. Pat. No. 8,880,799 on Nov. 4, 2014.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] NOT APPLICABLE
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT
DISC
[0004] NOT APPLICABLE
BACKGROUND OF THE INVENTION
Technical Field of the Invention
[0005] This invention relates generally to computing systems and
more particularly to data storage solutions within such computing
systems.
Description of Related Art
[0006] Computers are known to communicate, process, and store data.
Such computers range from wireless smart phones to data centers
that support millions of web searches, stock trades, or on-line
purchases every day. In general, a computing system generates data
and/or manipulates data from one form into another. For instance,
an image sensor of the computing system generates raw picture data
and, using an image compression program (e.g., JPEG, MPEG, etc.),
the computing system manipulates the raw picture data into a
standardized compressed image.
[0007] With continued advances in processing speed and
communication speed, computers are capable of processing real time
multimedia data for applications ranging from simple voice
communications to streaming high definition video. As such,
general-purpose information appliances are replacing purpose-built
communications devices (e.g., a telephone). For example, smart
phones can support telephony communications but they are also
capable of text messaging and accessing the internet to perform
functions including email, web browsing, remote applications
access, and media communications (e.g., telephony voice, image
transfer, music files, video files, real time video streaming.
etc.).
[0008] Each type of computer is constructed and operates in
accordance with one or more communication, processing, and storage
standards. As a result of standardization and with advances in
technology, more and more information content is being converted
into digital formats. For example, more digital cameras are now
being sold than film cameras, thus producing more digital pictures.
As another example, web-based programming is becoming an
alternative to over the air television broadcasts and/or cable
broadcasts. As further examples, papers, books, video
entertainment, home video, etc. are now being stored digitally,
which increases the demand on the storage function of
computers.
[0009] A typical computer storage system includes one or more
memory devices aligned with the needs of the various operational
aspects of the computer's processing and communication functions.
Generally, the immediacy of access dictates what type of memory
device is used. For example, random access memory (RAM) memory can
be accessed in any random order with a constant response time, thus
it is typically used for cache memory and main memory. By contrast,
memory device technologies that require physical movement such as
magnetic disks, tapes, and optical discs, have a variable response
time as the physical movement can take longer than the data
transfer, thus they are typically used for secondary memory (e.g.,
hard drive, backup memory, etc.).
[0010] A computer's storage system will be compliant with one or
more computer storage standards that include, but are not limited
to, network file system (NFS), flash file system (FFS), disk file
system (DFS), small computer system interface (SCSI), internet
small computer system interface (iSCSI), file transfer protocol
(FTP), and web-based distributed authoring and versioning (WebDAV).
These standards specify the data storage format (e.g., files, data
objects, data blocks, directories, etc.) and interfacing between
the computer's processing function and its storage system, which is
a primary function of the computer's memory controller.
[0011] Despite the standardization of the computer and its storage
system, memory devices fail; especially commercial grade memory
devices that utilize technologies incorporating physical movement
(e.g., a disc drive). For example, it is fairly common for a disc
drive to routinely suffer from bit level corruption and to
completely fail after three years of use. One solution is to
utilize a higher-grade disc drive, which adds significant cost to a
computer.
[0012] Another solution is to utilize multiple levels of redundant
disc drives to replicate the data into two or more copies. One such
redundant drive approach is called redundant array of independent
discs (RAID). In a RAID device, a RAID controller adds parity data
to the original data before storing it across the array. The parity
data is calculated from the original data such that the failure of
a disc will not result in the loss of the original data. For
example, RAID 5 uses three discs to protect data from the failure
of a single disc. The parity data, and associated redundancy
overhead data, reduces the storage capacity of three independent
discs by one third (e.g., n-1=capacity). RAID 6 can recover from a
loss of two discs and requires a minimum of four discs with a
storage capacity of n-2.
[0013] While RAID addresses the memory device failure issue, it is
not without its own failure issues that affect its effectiveness,
efficiency and security. For instance, as more discs are added to
the array, the probability of a disc failure increases, which
increases the demand for maintenance. For example, when a disc
fails, it needs to be manually replaced before another disc fails
and the data stored in the RAID device is lost. To reduce the risk
of data loss, data on a RAID device is typically copied on to one
or more other RAID devices. While this addresses the loss of data
issue, it raises a security issue since multiple copies of data are
available, which increases the chances of unauthorized access.
Further, as the amount of data being stored grows, the overhead of
RAID devices becomes a non-trivial efficiency issue.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] FIG. 1 is a schematic block diagram of an embodiment of a
computing system in accordance with the invention;
[0015] FIG. 2 is a schematic block diagram of an embodiment of a
computing core in accordance with the invention;
[0016] FIG. 3 is a schematic block diagram of an embodiment of a
distributed storage processing unit in accordance with the
invention;
[0017] FIG. 4 is a schematic block diagram of an embodiment of a
grid module in accordance with the invention;
[0018] FIG. 5 is a diagram of an example embodiment of error coded
data slice creation in accordance with the invention;
[0019] FIG. 6 is a flowchart illustrating the determination of a
data revision number;
[0020] FIG. 7 is a flowchart illustrating the retrieving of like
revision data;
[0021] FIG. 8 is a flowchart illustrating the storing of data;
[0022] FIG. 9 is another flowchart illustrating the storing of
data;
[0023] FIG. 10 is another flowchart illustrating the storing of
data;
[0024] FIG. 11 is a flowchart illustrating the deleting of data;
and
[0025] FIG. 12 is a flowchart illustrating the retrieving of
data
DETAILED DESCRIPTION OF THE INVENTION
[0026] FIG. 1 is a schematic block diagram of a computing system 10
that includes one or more of a first type of user devices 12, one
or more of a second type of user devices 14, at least one
distributed storage (DS) processing unit 16, at least one DS
managing unit 18, at least one storage integrity processing unit
20, and a distributed storage network (DSN) memory 22 coupled via a
network 24. The network 24 may include one or more wireless and/or
wire lined communication systems; one or more private intranet
systems and/or public interne systems; and/or one or more local
area networks (LAN) and/or wide area networks (WAN).
[0027] The DSN memory 22 includes a plurality of distributed
storage (DS) units 36 for storing data of the system. Each of the
DS units 36 includes a processing module and memory and may be
located at a geographically different site than the other DS units
(e.g., one in Chicago, one in Milwaukee, etc.). The processing
module may be a single processing device or a plurality of
processing devices. Such a processing device may be a
microprocessor, micro-controller, digital signal processor,
microcomputer, central processing unit, field programmable gate
array, programmable logic device, state machine, logic circuitry,
analog circuitry, digital circuitry, and/or any device that
manipulates signals (analog and/or digital) based on hard coding of
the circuitry and/or operational instructions. The processing
module may have an associated memory and/or memory element, which
may be a single memory device, a plurality of memory devices,
and/or embedded circuitry of the processing module. Such a memory
device may be a read-only memory, random access memory, volatile
memory, non-volatile memory, static memory, dynamic memory, flash
memory, cache memory, and/or any device that stores digital
information. Note that if the processing module includes more than
one processing device, the processing devices may be centrally
located (e.g., directly coupled together via a wired and/or
wireless bus structure) or may be distributedly located (e.g.,
cloud computing via indirect coupling via a local area network
and/or a wide area network). Further note that when the processing
module implements one or more of its functions via a state machine,
analog circuitry, digital circuitry, and/or logic circuitry, the
memory and/or memory element storing the corresponding operational
instructions may be embedded within, or external to, the circuitry
comprising the state machine, analog circuitry, digital circuitry,
and/or logic circuitry. Still further note that, the memory element
stores, and the processing module executes, hard coded and/or
operational instructions corresponding to at least some of the
steps and/or functions illustrated in FIGS. 1-12.
[0028] Each of the user devices 12-14, the DS processing unit 16,
the DS managing unit 18, and the storage integrity processing unit
20 may be a portable computing device (e.g., a social networking
device, a gaming device, a cell phone, a smart phone, a personal
digital assistant, a digital music player, a digital video player,
a laptop computer, a handheld computer, a video game controller,
and/or any other portable device that includes a computing core)
and/or a fixed computing device (e.g., a personal computer, a
computer server, a cable set-top box, a satellite receiver, a
television set, a printer, a fax machine, home entertainment
equipment, a video game console, and/or any type of home or office
computing equipment). Such a portable or fixed computing device
includes a computing core 26 and one or more interfaces 30, 32,
and/or 33. An embodiment of the computing core 26 will be described
with reference to FIG. 2.
[0029] With respect to the interfaces, each of the interfaces 30,
32, and 33 includes software and/or hardware to support one or more
communication links via the network 24 and/or directly. For
example, interface 30 supports a communication link (wired,
wireless, direct, via a LAN, via the network 24, etc.) between the
first type of user device 14 and the DS processing unit 16. As
another example, DSN interface 32 supports a plurality of
communication links via the network 24 between the DSN memory 22
and the DS processing unit 16, the first type of user device 12,
and/or the storage integrity processing unit 20. As yet another
example, interface 33 supports a communication link between the DS
managing unit 18 and any one of the other devices and/or units 12,
14, 16, 20, and/or 22 via the network 24.
[0030] In general, and with respect to data storage, the system 10
supports three primary functions: distributed network data storage
management, distributed data storage and retrieval, and data
storage integrity verification. In accordance with these three
primary functions, data can be distributedly stored in a plurality
of physically different locations and subsequently retrieved in a
reliable and secure manner regardless of failures of individual
storage devices, failures of network equipment, the duration of
storage, the amount of data being stored, attempts at hacking the
data, etc.
[0031] The DS managing unit 18 performs distributed network data
storage management functions, which include establishing
distributed data storage parameters, performing network operations,
performing network administration, and/or performing network
maintenance. The DS managing unit 18 establishes the distributed
data storage parameters (e.g., allocation of virtual DSN memory
space, distributed storage parameters, security parameters, billing
information, user profile information, etc.) for one or more of the
user devices 12-14 (e.g., established for individual devices,
established for a user group of devices, established for public
access by the user devices, etc.). For example, the DS managing
unit 18 coordinates the creation of a vault (e.g., a virtual memory
block) within the DSN memory 22 for a user device (for a group of
devices, or for public access). The DS managing unit 18 also
determines the distributed data storage parameters for the vault.
In particular, the DS managing unit 18 determines a number of
slices (e.g., the number that a data segment of a data file and/or
data block is partitioned into for distributed storage) and a read
threshold value (e.g., the minimum number of slices required to
reconstruct the data segment).
[0032] As another example, the DS managing unit 18 creates and
stores, locally or within the DSN memory 22, user profile
information. The user profile information includes one or more of
authentication information, permissions, and/or the security
parameters. The security parameters may include one or more of
encryption/decryption scheme, one or more encryption keys, key
generation scheme, and data encoding/decoding scheme.
[0033] As yet another example, the DS managing unit 18 creates
billing information for a particular user, user group, vault
access, public vault access, etc. For instance, the DS managing
unit 18 tracks the number of times a user accesses a private vault
and/or public vaults, which can be used to generate a per-access
bill. In another instance, the DS managing unit 18 tracks the
amount of data stored and/or retrieved by a user device and/or a
user group, which can be used to generate a per-data-amount
bill.
[0034] The DS managing unit 18 also performs network operations,
network administration, and/or network maintenance. As at least
part of performing the network operations and/or administration,
the DS managing unit 18 monitors performance of the devices and/or
units of the system 10 for potential failures, determines the
devices' and/or units' activation status, determines the devices'
and/or units' loading, and any other system level operation that
affects the performance level of the system 10. For example, the DS
managing unit 18 receives and aggregates network management alarms,
alerts, errors, status information, performance information, and
messages from the devices 12-14 and/or the units 16, 20, 22. For
example, the DS managing unit 18 receives a simple network
management protocol (SNMP) message regarding the status of the DS
processing unit 16.
[0035] The DS managing unit 18 performs the network maintenance by
identifying equipment within the system 10 that needs replacing,
upgrading, repairing, and/or expanding. For example, the DS
managing unit 18 determines that the DSN memory 22 needs more DS
units 36 or that one or more of the DS units 36 needs updating.
[0036] The second primary function (i.e., distributed data storage
and retrieval) begins and ends with a user device 12-14. For
instance, if a second type of user device 14 has a data file 38
and/or data block 40 to store in the DSN memory 22, it sends the
data file 38 and/or data block 40 to the DS processing unit 16 via
its interface 30. As will be described in greater detail with
reference to FIG. 2, the interface 30 functions to mimic a
conventional operating system (OS) file system interface (e.g.,
network file system (NFS), flash file system (FFS), disk file
system (DFS), file transfer protocol (FTP), web-based distributed
authoring and versioning (WebDAV), etc.) and/or a block memory
interface (e.g., small computer system interface (SCSI), internet
small computer system interface (iSCSI), etc.). In addition, the
interface 30 may attach a user identification code (ID) to the data
file 38 and/or data block 40.
[0037] The DS processing unit 16 receives the data file 38 and/or
data block 40 via its interface 30 and performs a distributed
storage (DS) process 34 thereon (e.g., an error coding dispersal
storage function). The DS processing 34 begins by partitioning the
data file 38 and/or data block 40 into one or more data segments,
which is represented as Y data segments. For example, the DS
processing 34 may partition the data file 38 and/or data block 40
into a fixed byte size segment (e.g., 2.sup.1 to 2.sup.n bytes,
where n=>2) or a variable byte size (e.g., change byte size from
segment to segment, or from groups of segments to groups of
segments, etc.).
[0038] For each of the Y data segments, the DS processing 34 error
encodes (e.g., forward error correction (FEC), information
dispersal algorithm, or error correction coding) and slices (or
slices then error encodes) the data segment into a plurality of
error coded (EC) data slices 42-48, which is represented as X
slices per data segment. The number of slices (X) per segment,
which corresponds to a number of pillars n, is set in accordance
with the distributed data storage parameters and the error coding
scheme. For example, if a Reed-Solomon (or other FEC scheme) is
used in an n/k system, then a data segment is divided into n
slices, where k number of slices is needed to reconstruct the
original data (i.e., k is the threshold). As a few specific
examples, the n/k factor may be 5/3; 6/4; 8/6; 8/5; 16/10.
[0039] For each EC slice 42-48, the DS processing unit 16 creates a
unique slice name and appends it to the corresponding EC slice
42-48. The slice name includes universal DSN memory addressing
routing information (e.g., virtual memory addresses in the DSN
memory 22) and user-specific information (e.g., user ID, file name,
data block identifier, etc.).
[0040] The DS processing unit 16 transmits the plurality of EC
slices 42-48 to a plurality of DS units 36 of the DSN memory 22 via
the DSN interface 32 and the network 24. The DSN interface 32
formats each of the slices for transmission via the network 24. For
example, the DSN interface 32 may utilize an internet protocol
(e.g., TCP/IP, etc.) to packetize the EC slices 42-48 for
transmission via the network 24.
[0041] The number of DS units 36 receiving the EC slices 42-48 is
dependent on the distributed data storage parameters established by
the DS managing unit 18. For example, the DS managing unit 18 may
indicate that each slice is to be stored in a different DS unit 36.
As another example, the DS managing unit 18 may indicate that like
slice numbers of different data segments are to be stored in the
same DS unit 36. For example, the first slice of each of the data
segments is to be stored in a first DS unit 36, the second slice of
each of the data segments is to be stored in a second DS unit 36,
etc. In this manner, the data is encoded and distributedly stored
at physically diverse locations to improve data storage integrity
and security. Further examples of encoding the data segments will
be provided with reference to one or more of FIGS. 2-12.
[0042] Each DS unit 36 that receives an EC slice 42-48 for storage
translates the virtual DSN memory address of the slice into a local
physical address for storage. Accordingly, each DS unit 36
maintains a virtual to physical memory mapping to assist in the
storage and retrieval of data.
[0043] The first type of user device 12 performs a similar function
to store data in the DSN memory 22 with the exception that it
includes the DS processing. As such, the device 12 encodes and
slices the data file and/or data block it has to store. The device
then transmits the slices 11 to the DSN memory via its DSN
interface 32 and the network 24.
[0044] For a second type of user device 14 to retrieve a data file
or data block from memory, it issues a read command via its
interface 30 to the DS processing unit 16. The DS processing unit
16 performs the DS processing 34 to identify the DS units 36
storing the slices of the data file and/or data block based on the
read command. The DS processing unit 16 may also communicate with
the DS managing unit 18 to verify that the user device 14 is
authorized to access the requested data.
[0045] Assuming that the user device is authorized to access the
requested data, the DS processing unit 16 issues slice read
commands to at least a threshold number of the DS units 36 storing
the requested data (e.g., to at least 10 DS units for a 16/10 error
coding scheme). Each of the DS units 36 receiving the slice read
command, verifies the command, accesses its virtual to physical
memory mapping, retrieves the requested slice, or slices, and
transmits it to the DS processing unit 16.
[0046] Once the DS processing unit 16 has received a read threshold
number of slices for a data segment, it performs an error decoding
function and de-slicing to reconstruct the data segment. When Y
number of data segments has been reconstructed, the DS processing
unit 16 provides the data file 38 and/or data block 40 to the user
device 14. Note that the first type of user device 12 performs a
similar process to retrieve a data file and/or data block.
[0047] The storage integrity processing unit 20 performs the third
primary function of data storage integrity verification. In
general, the storage integrity processing unit 20 periodically
retrieves slices 45, and/or slice names, of a data file or data
block of a user device to verify that one or more slices have not
been corrupted or lost (e.g., the DS unit failed). The retrieval
process mimics the read process previously described.
[0048] If the storage integrity processing unit 20 determines that
one or more slices is corrupted or lost, it rebuilds the corrupted
or lost slice(s) in accordance with the error coding scheme. The
storage integrity processing unit 20 stores the rebuilt slice, or
slices, in the appropriate DS unit(s) 36 in a manner that mimics
the write process previously described.
[0049] FIG. 2 is a schematic block diagram of an embodiment of a
computing core 26 that includes a processing module 50, a memory
controller 52, main memory 54, a video graphics processing unit 55,
an input/output (TO) controller 56, a peripheral component
interconnect (PCI) interface 58, an IO interface 60, at least one
IO device interface module 62, a read only memory (ROM) basic input
output system (BIOS) 64, and one or more memory interface modules.
The memory interface module(s) includes one or more of a universal
serial bus (USB) interface module 66, a host bus adapter (HBA)
interface module 68, a network interface module 70, a flash
interface module 72, a hard drive interface module 74, and a DSN
interface module 76. Note the DSN interface module 76 and/or the
network interface module 70 may function as the interface 30 of the
user device 14 of FIG. 1. Further note that the IO device interface
module 62 and/or the memory interface modules may be collectively
or individually referred to as IO ports.
[0050] The processing module 50 may be a single processing device
or a plurality of processing devices. Such a processing device may
be a microprocessor, micro-controller, digital signal processor,
microcomputer, central processing unit, field programmable gate
array, programmable logic device, state machine, logic circuitry,
analog circuitry, digital circuitry, and/or any device that
manipulates signals (analog and/or digital) based on hard coding of
the circuitry and/or operational instructions. The processing
module 50 may have an associated memory and/or memory element,
which may be a single memory device, a plurality of memory devices,
and/or embedded circuitry of the processing module 50. Such a
memory device may be a read-only memory, random access memory,
volatile memory, non-volatile memory, static memory, dynamic
memory, flash memory, cache memory, and/or any device that stores
digital information. Note that if the processing module 50 includes
more than one processing device, the processing devices may be
centrally located (e.g., directly coupled together via a wired
and/or wireless bus structure) or may be distributedly located
(e.g., cloud computing via indirect coupling via a local area
network and/or a wide area network). Further note that when the
processing module 50 implements one or more of its functions via a
state machine, analog circuitry, digital circuitry, and/or logic
circuitry, the memory and/or memory element storing the
corresponding operational instructions may be embedded within, or
external to, the circuitry comprising the state machine, analog
circuitry, digital circuitry, and/or logic circuitry. Still further
note that, the memory element stores, and the processing module 50
executes, hard coded and/or operational instructions corresponding
to at least some of the steps and/or functions illustrated in FIGS.
1-12.
[0051] FIG. 3 is a schematic block diagram of an embodiment of a
dispersed storage (DS) processing module 34 of user device 12
and/or of the DS processing unit 16. The DS processing module 34
includes a gateway module 78, an access module 80, a grid module
82, and a storage module 84. The DS processing module 34 may also
include an interface 30 and the DSnet interface 32 or the
interfaces 68 and/or 70 may be part of user device 12 or of the DS
processing unit 16. The DS processing module 34 may further include
a bypass/feedback path between the storage module 84 to the gateway
module 78. Note that the modules 78-84 of the DS processing module
34 may be in a single unit or distributed across multiple
units.
[0052] In an example of storing data, the gateway module 78
receives an incoming data object that includes a user ID field 86,
an object name field 88, and the data object field 40 and may also
receive corresponding information that includes a process
identifier (e.g., an internal process/application ID), metadata, a
file system directory, a block number, a transaction message, a
user device identity (ID), a data object identifier, a source name,
and/or user information. The gateway module 78 authenticates the
user associated with the data object by verifying the user ID 86
with the DS managing unit 18 and/or another authenticating
unit.
[0053] When the user is authenticated, the gateway module 78
obtains user information from the management unit 18, the user
device, and/or the other authenticating unit. The user information
includes a vault identifier, operational parameters, and user
attributes (e.g., user data, billing information, etc.). A vault
identifier identifies a vault, which is a virtual memory space that
maps to a set of DS storage units 36. For example, vault 1 (i.e.,
user 1's DSN memory space) includes eight DS storage units (X=8
wide) and vault 2 (i.e., user 2's DSN memory space) includes
sixteen DS storage units (X=16 wide). The operational parameters
may include an error coding algorithm, the width n (number of
pillars X or slices per segment for this vault), a read threshold
T, a write threshold, an encryption algorithm, a slicing parameter,
a compression algorithm, an integrity check method, caching
settings, parallelism settings, and/or other parameters that may be
used to access the DSN memory layer.
[0054] The gateway module 78 uses the user information to assign a
source name 35 to the data. For instance, the gateway module 78
determines the source name 35 of the data object 40 based on the
vault identifier and the data object. For example, the source name
may contain a file identifier (ID), a vault generation number, a
reserved field, and a vault identifier (ID). As another example,
the gateway module 78 may generate the file ID based on a hash
function of the data object 40. Note that the gateway module 78 may
also perform message conversion, protocol conversion, electrical
conversion, optical conversion, access control, user
identification, user information retrieval, traffic monitoring,
statistics generation, configuration, management, and/or source
name determination.
[0055] The access module 80 receives the data object 40 and creates
a series of data segments 1 through Y 90-92 in accordance with a
data storage protocol (e.g., file storage system, a block storage
system, and/or an aggregated block storage system). The number of
segments Y may be chosen or randomly assigned based on a selected
segment size and the size of the data object. For example, if the
number of segments is chosen to be a fixed number, then the size of
the segments varies as a function of the size of the data object.
For instance, if the data object is an image file of 4,194,304
eight bit bytes (e.g., 33,554,432 bits) and the number of segments
Y=131,072, then each segment is 256 bits or 32 bytes. As another
example, if segment size is fixed, then the number of segments Y
varies based on the size of data object. For instance, if the data
object is an image file of 4,194,304 bytes and the fixed size of
each segment is 4,096 bytes, then the number of segments Y=1,024.
Note that each segment is associated with the same source name.
[0056] The grid module 82 receives the data segments and may
manipulate (e.g., compression, encryption, cyclic redundancy check
(CRC), etc.) each of the data segments before performing an error
coding function of the error coding dispersal storage function to
produce a pre-manipulated data segment. After manipulating a data
segment, if applicable, the grid module 82 error encodes (e.g.,
Reed-Solomon, Convolution encoding, Trellis encoding, etc.) the
data segment or manipulated data segment into X error coded data
slices 42-44.
[0057] The value X, or the number of pillars (e.g., X=16), is
chosen as a parameter of the error coding dispersal storage
function. Other parameters of the error coding dispersal function
include a read threshold T, a write threshold W, etc. The read
threshold (e.g., T=10, when X=16) corresponds to the minimum number
of error-free error coded data slices required to reconstruct the
data segment. In other words, the DS processing module 34 can
compensate for X-T (e.g., 16-10=6) missing error coded data slices
per data segment. The write threshold W corresponds to a minimum
number of DS storage units that acknowledge proper storage of their
respective data slices before the DS processing module indicates
proper storage of the encoded data segment. Note that the write
threshold is greater than or equal to the read threshold for a
given number of pillars (X).
[0058] For each data slice of a data segment, the grid module 82
generates a unique slice name 37 and attaches it thereto. The slice
name 37 includes a universal routing information field and a vault
specific field and may be 48 bytes (e.g., 24 bytes for each of the
universal routing information field and the vault specific field).
As illustrated, the universal routing information field includes a
slice index, a vault ID, a vault generation, and a reserved field.
The slice index is based on the pillar number and the vault ID and,
as such, is unique for each pillar (e.g., slices of the same pillar
for the same vault for any segment will share the same slice
index). The vault specific field includes a data name, which
includes a file ID and a segment number (e.g., a sequential
numbering of data segments 1-Y of a simple data object or a data
block number).
[0059] Prior to outputting the error coded data slices of a data
segment, the grid module may perform post-slice manipulation on the
slices. If enabled, the manipulation includes slice level
compression, encryption, CRC, addressing, tagging, and/or other
manipulation to improve the effectiveness of the computing
system.
[0060] When the error coded data slices of a data segment are ready
to be outputted, the grid module 82 determines which of the DS
storage units 36 will store the EC data slices based on a dispersed
storage memory mapping associated with the user's vault and/or DS
storage unit attributes. The DS storage unit attributes may include
availability, self-selection, performance history, link speed, link
latency, ownership, available DSN memory, domain, cost, a
prioritization scheme, a centralized selection message from another
source, a lookup table, data ownership, and/or any other factor to
optimize the operation of the computing system. Note that the
number of DS storage units 36 is equal to or greater than the
number of pillars (e.g., X) so that no more than one error coded
data slice of the same data segment is stored on the same DS
storage unit 36. Further note that EC data slices of the same
pillar number but of different segments (e.g., EC data slice 1 of
data segment 1 and EC data slice 1 of data segment 2) may be stored
on the same or different DS storage units 36.
[0061] The storage module 84 performs an integrity check on the
outbound encoded data slices and, when successful, identifies a
plurality of DS storage units based on information provided by the
grid module 82. The storage module 84 then outputs the encoded data
slices 1 through X of each segment 1 through Y to the DS storage
units 36. Each of the DS storage units 36 stores its EC data
slice(s) and maintains a local virtual DSN address to physical
location table to convert the virtual DSN address of the EC data
slice(s) into physical storage addresses.
[0062] In an example of a read operation, the user device 12 and/or
14 sends a read request to the DS processing unit 16, which
authenticates the request. When the request is authentic, the DS
processing unit 16 sends a read message to each of the DS storage
units 36 storing slices of the data object being read. The slices
are received via the DSnet interface 32 and processed by the
storage module 84, which performs a parity check and provides the
slices to the grid module 82 when the parity check was successful.
The grid module 82 decodes the slices in accordance with the error
coding dispersal storage function to reconstruct the data segment.
The access module 80 reconstructs the data object from the data
segments and the gateway module 78 formats the data object for
transmission to the user device.
[0063] FIG. 4 is a schematic block diagram of an embodiment of a
grid module 82 that includes a control unit 73, a pre-slice
manipulator 75, an encoder 77, a slicer 79, a post-slice
manipulator 81, a pre-slice de-manipulator 83, a decoder 85, a
de-slicer 87, and/or a post-slice de-manipulator 89. Note that the
control unit 73 may be partially or completely external to the grid
module 82. For example, the control unit 73 may be part of the
computing core at a remote location, part of a user device, part of
the DS managing unit 18, or distributed amongst one or more DS
storage units.
[0064] In an example of a write operation, the pre-slice
manipulator 75 receives a data segment 90-92 and a write
instruction from an authorized user device. The pre-slice
manipulator 75 determines if pre-manipulation of the data segment
90-92 is required and, if so, what type. The pre-slice manipulator
75 may make the determination independently or based on
instructions from the control unit 73, where the determination is
based on a computing system-wide predetermination, a table lookup,
vault parameters associated with the user identification, the type
of data, security requirements, available DSN memory, performance
requirements, and/or other metadata.
[0065] Once a positive determination is made, the pre-slice
manipulator 75 manipulates the data segment 90-92 in accordance
with the type of manipulation. For example, the type of
manipulation may be compression (e.g., Lempel-Ziv-Welch, Huffman,
Golomb, fractal, wavelet, etc.), signatures (e.g., Digital
Signature Algorithm (DSA), Elliptic Curve DSA, Secure Hash
Algorithm, etc.), watermarking, tagging, encryption (e.g., Data
Encryption Standard, Advanced Encryption Standard, etc.), adding
metadata (e.g., time/date stamping, user information, file type,
etc.), cyclic redundancy check (e.g., CRC32), and/or other data
manipulations to produce the pre-manipulated data segment.
[0066] The encoder 77 encodes the pre-manipulated data segment 92
using a forward error correction (FEC) encoder (and/or other type
of erasure coding and/or error coding) to produce an encoded data
segment 94. The encoder 77 determines which forward error
correction algorithm to use based on a predetermination associated
with the user's vault, a time based algorithm, user direction, DS
managing unit direction, control unit direction, as a function of
the data type, as a function of the data segment 92 metadata,
and/or any other factor to determine algorithm type. The forward
error correction algorithm may be Golay, Multidimensional parity,
Reed-Solomon, Hamming, Bose Ray Chauduri Hocquenghem (BCH),
Cauchy-Reed-Solomon, or any other FEC encoder. Note that the
encoder 77 may use a different encoding algorithm for each data
segment 92, the same encoding algorithm for the data segments 92 of
a data object, or a combination thereof.
[0067] The encoded data segment 94 is of greater size than the data
segment 92 by the overhead rate of the encoding algorithm by a
factor of X/T, where X is the width or number of slices, and T is
the read threshold. In this regard, the corresponding decoding
process can accommodate at most X-T missing EC data slices and
still recreate the data segment 92. For example, if X=16 and T=10,
then the data segment 92 will be recoverable as long as 10 or more
EC data slices per segment are not corrupted.
[0068] The slicer 79 transforms the encoded data segment 94 into EC
data slices in accordance with the slicing parameter from the vault
for this user and/or data segment 92. For example, if the slicing
parameter is X=16, then the slicer 79 slices each encoded data
segment 94 into 16 encoded slices.
[0069] The post-slice manipulator 81 performs, if enabled,
post-manipulation on the encoded slices to produce the EC data
slices. If enabled, the post-slice manipulator 81 determines the
type of post-manipulation, which may be based on a computing
system-wide predetermination, parameters in the vault for this
user, a table lookup, the user identification, the type of data,
security requirements, available DSN memory, performance
requirements, control unit directed, and/or other metadata. Note
that the type of post-slice manipulation may include slice level
compression, signatures, encryption, CRC, addressing, watermarking,
tagging, adding metadata, and/or other manipulation to improve the
effectiveness of the computing system.
[0070] In an example of a read operation, the post-slice
de-manipulator 89 receives at least a read threshold number of EC
data slices and performs the inverse function of the post-slice
manipulator 81 to produce a plurality of encoded slices. The
de-slicer 87 de-slices the encoded slices to produce an encoded
data segment 94. The decoder 85 performs the inverse function of
the encoder 77 to recapture the data segment 90-92. The pre-slice
de-manipulator 83 performs the inverse function of the pre-slice
manipulator 75 to recapture the data segment 90-92.
[0071] FIG. 5 is a diagram of an example of slicing an encoded data
segment 94 by the slicer 79. In this example, the encoded data
segment 94 includes thirty-two bits, but may include more or less
bits. The slicer 79 disperses the bits of the encoded data segment
94 across the EC data slices in a pattern as shown. As such, each
EC data slice does not include consecutive bits of the data segment
94 reducing the impact of consecutive bit failures on data
recovery. For example, if EC data slice 2 (which includes bits 1,
5, 9, 13, 17, 25, and 29) is unavailable (e.g., lost, inaccessible,
or corrupted), the data segment can be reconstructed from the other
EC data slices (e.g., 1, 3 and 4 for a read threshold of 3 and a
width of 4).
[0072] FIG. 6 is a flowchart illustrating the determination of a
data revision number where the DS processing determines the
revision number and appends it to, or associates it with EC data
slices being distributedly stored. The DS processing subsequent
retrieval of EC data slices verifies that the slices utilized to
recreate the data segment have the same appended revision number to
improve data consistency and system performance. The retrieval
method will be discussed in greater detail with reference to FIG.
7.
[0073] The method 600 begins with the step 602 where the DS
processing creates EC data slices for a data segment in accordance
with the operational parameters as previously discussed. As
illustrated by block 604, the DS processing determines the revision
number for the slices of the data segment based on one or more of a
timestamp, a random number, the user vault ID, the user ID, the
data object ID, a hash of the data object, and/or a hash of the
data object ID. For example, the revision number may be eight bytes
and comprise a UNIX time timestamp and a random number (e.g., to
provide an improvement of a unique revision number when data is
stored at the same time).
[0074] As illustrated by block 606, the DS processing appends the
revision number to each pillar slice of the same data segment such
that each pillar slice of the same data segment has the same
revision number. In an embodiment, the DS processing appends the
same revision number to all the slices of all the data segments of
the data object. In another embodiment, the DS processing appends
the same revision number to all the slices of each data segment but
the revision numbers from data segment to data segment of the data
object are different.
[0075] As illustrated by block 608, the DS processing determines
the DS units to send the slices to in accordance with the virtual
DSN address to physical location table for the user vault of the
data object.
[0076] As illustrated by block 610, the DS processing sends a write
command and slices with the appended revision number to the DS
units such that the DS units will store the slices and send a write
confirmation message to the DS processing in response. Note that
the slices are substantially sent in parallel from the DS
processing to the DS units via similar or different portions of the
network. Networks are known to fail from time to time thus all of
the DS units may not receive the slices. As a result of network
failures and other potential issues, the DS units may contain
slices with different revision numbers for the same data object
and/or data segment.
[0077] The DS processing receives the write confirmation message
from the DS units. The DS processing determines a write threshold
(e.g., from the user vault, a command, a predetermination) where
the write threshold is the minimum number of pillars required to
store the unique slices of the same data segment to meet the
criteria of a favorable write sequence. The write threshold is less
than the pillar width n and greater than the read threshold
(discussed previously).
[0078] As illustrated by blocks 612 and 616, the DS processing
determines if the number of received write confirmation messages is
equal to or greater than the write threshold. The determination may
be based on one or more of comparing the number of received write
confirmations to the write threshold, a command, a
predetermination, and/or a system performance indicator. The DS
processing may continue to keep checking for new write
confirmations when the DS processing determines that the number of
received write confirmation messages is not equal to or greater
than the write threshold. As further illustrated by block 616, the
DS processing may fail the write sequence if a predetermined period
of time expires before the DS processing determines that the number
of received write confirmation messages is equal to or greater than
the write threshold.
[0079] As illustrated by blocks 614, the DS processing sends a
write commit command to the DS units when the DS processing
determines that the number of received write confirmation messages
is equal to or greater than the write threshold. The DS unit makes
the slice visible on subsequent retrievals when the DS unit
receives the write commit command for slices the DS unit has write
confirmed.
[0080] The DS unit may request the slice be resent from the DS
processing when the DS unit receives the write commit command for
slices the DS unit has not write confirmed. The DS processing sends
the write command and slices with the appended revision number to
the DS units such that the DS units will store the slices and send
a write confirmation message to the DS processing in response when
the DS processing receives the slice request from the DS unit.
[0081] FIG. 7 is a flowchart illustrating the retrieving of like
revision data where the DS processing retrieves slices from the DS
unit pillars and verifies that the slices have the same appended
revision numbers to improve data consistency.
[0082] According to method 700, at block 702 the DS processing
determines the DS units (the pillars) to retrieve slices from in
accordance with the virtual DSN address to physical location table
for the user vault of the data object. As further illustrated by
block 702, the DS processing sends a retrieve command message to
the DS units where the message includes the slice name. The DS
processing sends the retrieve command to at least a read threshold
number of DS units. For example, the DS processing sends the
retrieve command to ten DS units in a 16/10 DSN system. In another
example, the DS processing sends the retrieve command to twelve DS
units in a 16/10 DSN system to provide better performance. The DS
processing may create and temporarily save a list of DS units that
were sent the retrieve command such that the DS processing may
choose different DS units in a subsequent retrieval attempt if the
present retrieval attempt fails. DS units send the slice and
appended revision number corresponding the slice name to the DS
processing when the DS unit receives the retrieval command
message.
[0083] As illustrated by block 704, the DS processing receives the
slices and appended revision number from the DS units. The DS
processing determines the number of received slices by counting
them. The DS processing determines the read threshold number for
this vault by retrieving the read threshold number form the vault.
The DS processing proceeds to the next step when the DS processing
determines that at least a read threshold number of slices have
been received from the DS units.
[0084] As illustrated by blocks 706 and 708, the DS processing
determines if the appended revision numbers for the slices from
each of the DS units are the same by comparing the revision
numbers. Note that it is possible for some of the revision numbers
to be different (e.g., as a result of a failure of a previous write
sequence or some other DS unit failure).
[0085] As illustrated by block 710, the DS processing determines
different DS units to send retrieval commands and the DS processing
sends the retrieve command to at least a read threshold number of
DS units when the appended revision numbers for the slices from
each of the current DS units are not the same. The determination
may be based on which DS units were already tried (saved
previously) and which of those were in a majority where the
majority had the same revision number. In such a scenario, the DS
processing need only send a retrieval command message to a smaller
set of DS units that have not been tried yet. The method branches
to the step of the DS processing receiving a read threshold number
of slices with appended revision numbers from the DS units.
[0086] As illustrated by block 712, the DS processing de-slices and
decodes the slices to produce the data segment when the appended
revision numbers for the slices from each of the current DS units
are the same.
[0087] FIG. 8 is a flowchart illustrating the storing of data where
the DS processing utilizes a transaction process to improve data
consistency.
[0088] The method 800 begins at block 802, where the DS processing
receives a data object to store (e.g., from the user device). As
illustrated by block 804, the DS processing creates the slices in
accordance with the operational parameters and appends revision
numbers created as previously discussed with reference to FIG. 6.
The DS processing determines the DS units and sends a write command
and the slices with the appended revision numbers. The
determination may be based on the virtual DSN address to physical
location table.
[0089] As further illustrated by block 804, the DS unit sends a
write command confirmation message to the DS processing in response
to receiving the write command. The DS processing receives the
write command confirmation messages, counts them, and determines if
a write threshold number of confirmations has been received by
comparing the count of received write command confirmation messages
to the write threshold. The DS processing sends a write commit
command to the DS units where the DS processing received a write
command confirmation message. Note that now the newest revision is
successfully stored in the DSN.
[0090] In the next steps, the DS processing stores the directory in
the DSN memory where the directory links the user root file to the
data object to the slice name and revisions. In other words, the
directory maps the data object to locations of encoded data slices
generated from the data objects. These locations may be virtual DSN
addresses, such as a source name or slice name that is further
translated, e.g., via a lookup in a virtual DSN address to physical
location table, to the DS unit locations, e.g., DS unit
identifier.
[0091] As illustrated by block 808, the DS processing determines
the current directory (e.g., reading it in the DS processing file
system, receiving it from the user device, etc.) and caches it
locally in the DS processing. As shown at block 810, the DS
processing creates slices for the current directory and sends the
slices with the write command and a revision number (e.g., the
directory is assigned a revision number) to the DS units associated
with the user vault. After caching the current directory, and
before sending the directory slices to be stored, a new entry can
be added to represent the directory slices. The DS units receive
the slices and write command and will process the write sequence as
will be discussed in greater with reference to FIG. 9.
[0092] As illustrated by blocks 812 and 814, the DS processing
determines the response from the DS units where the response may be
a write failure or a write success (e.g., a write command
confirmation). The write failure may result from one or more of the
slice names were already write locked (e.g., an active write
transaction was already in process), the DS processing determines
that the number of write confirmations is below the write
threshold, and/or the number of write confirmations with the same
revision numbers is below the write threshold.
[0093] As illustrated by block 814, the DS processing branches back
to the step of determining the directory when the DS processing
determines the response from the DS units is a write failure.
[0094] As illustrated by block 816, the DS processing sends a write
commit command to the DS units where the DS processing received
successful write confirmations when the DS processing determines
the response from the DS units is a write success. Note that this
step will activate the revision of the current directory.
[0095] FIG. 9 is another flowchart illustrating the storing of data
where the DS unit processes write transactions in accordance with a
transaction process to improve the consistency of stored data.
[0096] The method 900 begins at block 902, where the DS unit
receives a write command, slice name, revision number, and slice
for storage. The DS unit may determine if this slice name is
already in a write locked state (e.g., in an active write sequence)
by a lookup. The DS unit may send a write lock failure message to
the DS processing when the DS unit determines that this slice name
is already in a write locked state.
[0097] As illustrated by block 904, the DS unit may invoke write
lock (e.g., write in a local table for this slice name) for this
slice name when the DS unit determines that this slice name is not
already in a write locked state.
[0098] As illustrated by block 906, the DS unit stores the slice
and revision and sends a write confirmation command message to the
DS processing where the message includes the write confirmation,
the slice name, and the revision.
[0099] As illustrated by block 908, the DS unit starts a rollback
timer where the time value may be determined by the DS unit based
on a predetermined value (e.g., a lookup) or a variable value based
in part on a system performance indicator. For example, a longer
rollback timer may be determined when the system performance
indicator indicates that the system is busier than the average.
[0100] As illustrated by block 910, the DS unit determines if the
write commit command has been received from the DS processing when
the rollback timer is active. As illustrated by block 912, the DS
unit removes the write lock and makes the slice visible in
subsequent retrievals when the DS unit determines that a receive
commit was received while the rollback timer is active.
[0101] As illustrated by block 914, the DS unit determines if the
rollback timer has expired when the DS unit determines that a
receive commit has not been received while the rollback timer is
active. The DS unit branches back to the step of determining if a
write commit command has been received when the DS unit determines
that the rollback timer has not expired.
[0102] As illustrated by block 916, the DS unit rolls back the
version to the previous slice version (e.g., subsequent retrievals
will provide the last version, not the current version), removes
the write lock for this slice name, and may delete the current
version when the DS unit determines that the rollback timer has
expired.
[0103] Generally, after a write the DS unit may either commit or
rollback. A rollback may be implemented in response to a rollback
request, or in response to a failure to receive a commit command.
Both a commit and a rollback result in the write lock for the slice
being removed. In other embodiments, the same behavior as receiving
a rollback request, can be implemented using an inactivity timer.
In various embodiments, rolling back a request does not necessarily
restore a slice to its previous version, because in general the
state of the latest slice is changed using a commit procedure.
Instead any temporary memory used for holding an uncommitted slice
is freed. Also, when a slice is committed, any previous revisions
for that slice continue to exist.
[0104] FIG. 10 is another flowchart illustrating the storing of
data where the DS unit stores a revision.
[0105] The method 1000 begins at block 1002, with the DS unit
receiving a write command, slice name, slice, and revision from the
DS processing. As illustrated by block 1004, the DS unit determines
a local timestamp where in an embodiment the timestamp may be a
UNIX time timestamp.
[0106] As illustrated by block 1006, the DS unit stores the slice,
revision, and timestamp. Note that the DS unit may not delete
previous revisions of slices of the same data object such that the
data object may be subsequently retrieved from previous revisions
based in part on the timestamp.
[0107] FIG. 11 is a flowchart illustrating the deleting of data
where the DS unit processes a delete sequence for a revision.
[0108] The method 1100 begins at block 1102 with the DS unit
receiving a delete command, slice name, and revision from the DS
processing. In various embodiments, delete commands may not be
used; instead a write command is used to cause the DS unit to
"write" a delete marker. As illustrated at block 1104, the DS unit
determines a local timestamp where in an embodiment the timestamp
may be a UNIX time timestamp.
[0109] As illustrated as block 1106, the DS unit appends the
timestamp and a delete marker to the slice. Note that the DS unit
may not delete the slice in favor of marking when the delete
command was received. In another embodiment, the DS unit deletes
selective slices to free up memory while preserving at least a read
threshold number of slices per data such that the data object may
be subsequently retrieved from previous revisions based in part on
the timestamp.
[0110] FIG. 12 is a flowchart illustrating the retrieving of data
where the DS unit retrieves a particular revision of a data segment
(e.g., of a data object) based in part on the timestamp. In other
words, the DS unit will retrieve sluices of a snapshot of the data
object.
[0111] The method 1200 begins at block 1202 with the DS unit
receiving a read command, slice name, and timeframe from a
requester (e.g., the DS processing unit, the DS managing unit, the
storage integrity processing unit, or the user device). Note that
the timeframe may or may not be exactly aligned with timestamps
associated with previous revisions. As illustrated by block 1204,
the DS unit determines which local timestamp is closest to the
timeframe based on a comparison of timestamps to the timeframe.
[0112] As illustrated by block 1206, the DS unit determines the
slice for the timestamp based on a lookup. Note that this slice
revision represents the snapshot closest to the received timeframe.
As illustrated at block 1208, the DS unit retrieves the slice and
revision and sends the slice and revision to the requester.
[0113] In some embodiments, a read request returns all available
revisions, rather than a specific version or versions associated
with a specific time frame. When all revisions are returned in
response to a read request, the DS processing unit can determine
the best way to handle the various revisions received.
[0114] As may be used herein, the terms "substantially" and
"approximately" provides an industry-accepted tolerance for its
corresponding term and/or relativity between items. Such an
industry-accepted tolerance ranges from less than one percent to
fifty percent and corresponds to, but is not limited to, component
values, integrated circuit process variations, temperature
variations, rise and fall times, and/or thermal noise. Such
relativity between items ranges from a difference of a few percent
to magnitude differences. As may also be used herein, the term(s)
"coupled to" and/or "coupling" and/or includes direct coupling
between items and/or indirect coupling between items via an
intervening item (e.g., an item includes, but is not limited to, a
component, an element, a circuit, and/or a module) where, for
indirect coupling, the intervening item does not modify the
information of a signal but may adjust its current level, voltage
level, and/or power level. As may further be used herein, inferred
coupling (i.e., where one element is coupled to another element by
inference) includes direct and indirect coupling between two items
in the same manner as "coupled to". As may even further be used
herein, the term "operable to" indicates that an item includes one
or more of power connections, input(s), output(s), etc., to perform
one or more its corresponding functions and may further include
inferred coupling to one or more other items. As may still further
be used herein, the term "associated with", includes direct and/or
indirect coupling of separate items and/or one item being embedded
within another item. As may be used herein, the term "compares
favorably", indicates that a comparison between two or more items,
signals, etc., provides a desired relationship. For example, when
the desired relationship is that signal 1 has a greater magnitude
than signal 2, a favorable comparison may be achieved when the
magnitude of signal 1 is greater than that of signal 2 or when the
magnitude of signal 2 is less than that of signal 1.
[0115] The present invention has also been described above with the
aid of method steps illustrating the performance of specified
functions and relationships thereof. The boundaries and sequence of
these functional building blocks and method steps have been
arbitrarily defined herein for convenience of description.
Alternate boundaries and sequences can be defined so long as the
specified functions and relationships are appropriately performed.
Any such alternate boundaries or sequences are thus within the
scope and spirit of the claimed invention.
[0116] The present invention has been described above with the aid
of functional building blocks illustrating the performance of
certain significant functions. The boundaries of these functional
building blocks have been arbitrarily defined for convenience of
description. Alternate boundaries could be defined as long as the
certain significant functions are appropriately performed.
Similarly, flow diagram blocks may also have been arbitrarily
defined herein to illustrate certain significant functionality. To
the extent used, the flow diagram block boundaries and sequence
could have been defined otherwise and still perform the certain
significant functionality. Such alternate definitions of both
functional building blocks and flow diagram blocks and sequences
are thus within the scope and spirit of the claimed invention. One
of average skill in the art will also recognize that the functional
building blocks, and other illustrative blocks, modules and
components herein, can be implemented as illustrated or by discrete
components, application specific integrated circuits, processors
executing appropriate software and the like or any combination
thereof.
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