DISTRIBUTED STORAGE REVISION ROLLBACKS

• US 20110107036A1
• Filed: 07/16/2010
• Published: 05/05/2011
• Est. Priority Date: 10/29/2009
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Dhuse, Greg, Volvovski, Ilya, Resch, Jason K., Leggette, Wesley, Baptist, Andrew
• Granted Patent: US 9,015,431 B2
• Time in Patent Office: Days
• US Class Current: 711/154
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 2211/1028 Distributed, i.e. distributed RAID systems with parity
• CPC Class Codes: H04L 12/00 Data switching networks interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units G06F13/00
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

Multiple revisions of an encoded data slice can be stored in a distributed storage unit. Before writing a new revision of an encoded data slice to storage, the distributed storage unit can invoke a write lock for all encoded data slices having the same slice name as the slice being currently written. The slice being currently written can be stored in temporary storage, and a rollback timer started. If a commit command is received before expiration of the rollback timer, the currently written slice can be permanently stored and made accessible for read requests. If the rollback timer expires prior to the storage unit receiving a commit command, however, a previously stored revision will be used.

Claims

1. A method for use in a distributed storage unit, the method comprising:

storing a received encoded data slice in a memory associated with a distributed storage unit, the received encoded data slice having a slice name and a revision number;

starting a rollback timer indicating a period of time to wait for a commit command;

in response to receiving a commit command before expiration of the period of time, making the received encoded data slice available for access; and

in response to failing to receive a commit command before expiration of the period of time, making a previously stored revision of the received encoded data slice available for access.

2. The method of claim 1, further comprising:

receiving, in conjunction with the received encoded data slice, the slice name, the revision number, and a write command directing the distributed storage unit to store the received encoded data slice; and

sending a write confirmation in response to the storing.

3. The method of claim 2, further comprising:

invoking a write lock based on the slice name in response to the receiving; and

in response to receiving a commit command before expiration of the period of time, making the received encoded data slice available for access by releasing the write lock.

4. The method of claim 1, further comprising:

prior to the storing, checking a write lock status to determine if a write lock associated with the slice name is set; and

sending a fail message in response to determining that a write lock associated with the slice name is set.

5. The method of claim 1, further comprising:

in response to failing to receive a commit command before expiration of the period of time, deleting the received encoded data slice and removing a write lock associated with the slice name of the received encoded data slice.

6. A distributed storage unit comprising:

an interface to receive an encoded data slice having a slice name and a revision number;

a memory coupled to the interface, the memory to store the encoded data slice;

a processor to;

implement a rollback timer indicating a period of time to wait for a commit command;

exposing the received encoded data slice for access if the commit command is received before expiration of the rollback timer; and

exposing a previously stored revision of the encoded data slice available for access if the commit command is not received before expiration of the rollback timer.

7. The distributed storage unit of claim 6, further comprising:

the interface further to receive the slice name, the revision number, and a write command directing the distributed storage unit to store the received encoded data slice; and

the processor further to send a write confirmation in response to the interface receiving the encoded data slice.

8. The distributed storage unit of claim 7, the processor further to:

set a write lock indicator based on the slice name in response to the receiving; and

release the write lock indicator in response to receiving the commit command before expiration of the rollback timer.

9. The distributed storage unit of claim 6, further comprising:

the processor to check a status of a write lock indicator in response to the interface receiving the encoded data slice; and

the interface to send a fail message in response the status of the write lock indicator indicating that a write lock is active for the slice name.

10. The distributed storage unit of claim 6, further comprising:

if a commit command is not received before expiration of the rollback timer, the processor further to;

delete the encoded data slice; and

reset a write lock indicator associated with the slice name of the received encoded data slice.

11. A method for use in a distributed storage unit, the method comprising:

storing a first revision of an encoded data slice in a memory of a distributed storage unit, the first revision of an encoded data slice having a slice name and a revision number;

receiving a second revision of the encoded data slice to be stored in the memory of the distributed storage unit, the second revision of the encoded data slice having the same slice name as the first revision of the encoded data slice, but a different revision number;

temporarily storing the second revision of the encoded data slice;

starting a rollback timer indicating a period of time in which a commit command is expected to be received;

determining if a commit command is received before expiration of the rollback timer; and

in response to a favorable determination, replacing the first revision of the encoded data slice with the second revision of the encoded data slice.

12. The method of claim 11, wherein the replacing the first revision with the second revision comprises:

making the second revision of the encoded data slice accessible for reading in response to read requests for the encoded data slice.

13. The method of claim 11, further comprising:

receiving, in conjunction with the second revision of the encoded data slice, the slice name, a revision number associated with the second revision of the encoded data slice, and a write command directing the distributed storage unit to store the second revision of the encoded data slice; and

sending a write confirmation to a distributed storage processing unit indicating that the second revision of the encoded data slice has been temporarily stored.

14. The method of claim 13, further comprising:

preventing write access to encoded data slices having the same slice name as the second revision of the encoded data slice during a time when the rollback timer is unexpired and a commit command has not been processed by the distributed storage unit.

15. The method of claim 11, further comprising:

prior to the temporarily storing, determining if a write lock associated with the slice name is set; and

sending a fail message in response to a positive determination.

16. The method of claim 11, further comprising:

in response to an unfavorable determination, deleting the second revision of the encoded data slice and keeping the first revision accessible for reading in response to read requests for the encoded data slice

20. The distributed storage unit of claim 13, further comprising:

preventing write access to encoded data slices having the same slice name as the second revision of the encoded data slice during a time when the rollback timer is unexpired and a commit command has not been processed by the distributed storage unit.

17. A distributed storage unit comprising:

a processor to store a first revision of an encoded data slice in a memory of a distributed storage unit, the first revision of an encoded data slice having a slice name and a revision number;

an interface to receive a second revision of the encoded data slice to be stored in the memory of the distributed storage unit, the second revision of the encoded data slice having the same slice name as the first revision of the encoded data slice, but a different revision number;

a memory to temporarily store the second revision of the encoded data slice;

the processor further to;

start a rollback timer indicating a period of time in which a commit command is expected to be received;

determine if a commit command is received before expiration of the rollback timer; and

replace the first revision of the encoded data slice with the second revision of the encoded data slice in response to a favorable determination.

18. The distributed storage unit of claim 17, wherein:

the processor is further to make the second revision of the encoded data slice accessible for reading in response to read requests for the encoded data slice.

19. The distributed storage unit of claim 17, further comprising:

the interface to receive, in conjunction with the second revision of the encoded data slice, the slice name, a revision number associated with the second revision of the encoded data slice, and a write command directing the distributed storage unit to store the second revision of the encoded data slice; and

the interface to send a write confirmation to a distributed storage processing unit indicating that the second revision of the encoded data slice has been temporarily stored.