Method and system for service-aware parity placement in a storage system

• US 8,949,692 B1
• Filed: 01/23/2014
• Issued: 02/03/2015
• Est. Priority Date: 01/23/2014
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: DSSD, Inc. (Dell Technologies Inc.)
• Inventors: Bonwick, Jeffrey S.
• Primary Examiner(s): Alphonse, Fritz
• Application Number:
  US14/162,250
• Time in Patent Office: 376 Days
• Field of Search: 714/766, 714/710, 714/718, 714/47, 714/38, 714/5, 714/6.1
• US Class Current: 714/766
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1096 Parity calculation or recalculation after configuration or reconfiguration of the system
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/262 configured as RAID
• CPC Class Codes: G06F 2212/403 Error protection encoding, e.g. using parity or ECC codes
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0634 by changing the state or mode of one or more devices
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0673 Single storage device
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method and system for service-aware parity placement in a storage system, including after receiving the service notification specifying a target SD: writing a RAID stripe to the persistent storage, where the parity block of the RAID stripe is stored on the target SD and none of the data blocks in the RAID stripe are stored on the target SD. The method further includes performing a modified garbage collection operation that includes identifying a live RAID stripe in the persistent storage, writing a new RAID stripe to a new location in the persistent storage, where the new RAID stripe includes a copy of at least a portion of data from the live RAID stripe and a parity block in the new RAID stripe is stored on the target SD, and issuing a removal notification when the modified garbage collection operation is completed.

Claims

1. A non-transitory computer readable medium comprising instructions, which when executed by a processor perform a method, the method comprising:

receiving a service notification specifying a target storage device (SD), wherein the target SD is one of plurality of SDs;

after receiving the service notification;

receiving a request to write data to persistent storage, wherein the persistent storage comprises the plurality of SDs;

in response to the request, writing a Redundant Array of Independent Disks (RAID) stripe to the persistent storage wherein the RAID stripe comprises first data blocks and a first parity block, wherein at least one of the first data blocks comprises a portion of the data, wherein the first parity block comprises a parity value calculated using the first data blocks, and wherein the first parity block is stored on the target SD, and wherein none of the first data blocks are stored on the target SD;

performing a modified garbage collection operation, wherein the modified garbage collection operation comprises;

identifying a live RAID stripe in the persistent storage, wherein the live RAID stripe comprises second data blocks and a second parity block;

writing a new RAID stripe to a new location in the persistent storage, wherein the new RAID stripe comprises a third parity block and third data blocks, wherein at least one of the third data blocks stores a copy of a portion of data from the live RAID stripe, wherein the third parity block is stored on the target SD, and wherein none of the third data blocks is stored on the target SD; and

issuing a removal notification when the modified garbage collection operation is completed, wherein the removal notification indicates that the target SD may be removed from the persistent storage.

2. The non-transitory computer readable medium of claim 1, wherein the live RAID stripe was stored in the persistent storage prior to receiving the service notification.

3. The non-transitory computer readable medium of claim 1, wherein the second data blocks and the second parity block are arranged according to a RAID stripe geometry.

4. The non-transitory computer readable medium of claim 3, wherein the RAID stripe geometry specifies that the second parity block is located on the target SD.

5. The non-transitory computer readable medium of claim 4, wherein the third parity block comprises a third parity value, wherein the third parity value is a copy of a second parity value in the second parity block.

6. The non-transitory computer readable medium of claim 3, wherein the RAID geometry specifies that the second parity block is not located on the target SD.

7. The non-transitory computer readable medium of claim 6, wherein the new RAID stripe is associated with a second RAID stripe geometry, wherein the second RAID stripe geometry specifies that the third parity block is located on the target SD.

8. The non-transitory computer readable medium of claim 7, wherein the third parity block comprises a third parity value calculated using the third data blocks.

9. The non-transitory computer readable medium of claim 1, wherein the new RAID stripe further comprises a fourth parity block, wherein the fourth parity block is not stored on the target SD.

10. The non-transitory computer readable medium of claim 9, wherein the third parity block comprises a Q parity value and the fourth parity block comprises a P parity value.

11. The non-transitory computer readable medium of claim 1, wherein at least one the plurality of SDs is a solid state memory device.

12. The non-transitory computer readable medium of claim 1, wherein all live RAID stripes in the persistent storage are processed by the modified garbage collection operation, wherein all live RAID stripes were stored in the persistent storage prior to the service notification, and wherein the live RAID stripe is one of the live RAID stripes.

13. A system, comprising:

a storage array comprising a plurality of storage devices (SDs); and

a storage controller operatively connected to the storage array and configured to;

identify a target SD to remove;

after identifying the target SD, wherein the target SD is one of the plurality of SDs;

receive a request to write data to the storage array;

in response to the request, write a Redundant Array of Independent Disks (RAID) stripe to persistent storage, wherein the RAID stripe comprises data blocks and a first parity block, wherein at least one of the data blocks comprises a portion of the data, wherein the first parity block comprises a parity value calculated using the data blocks, and wherein the first parity block is stored on the target SD and wherein none of the data blocks are stored on the target SD;

perform a modified garbage collection operation, wherein the modified garbage collection operation comprises;

identifying a live RAID stripe in the persistent storage, wherein the live RAID stripe comprises second data blocks and a second parity block;

writing a new RAID stripe to a new location in the persistent storage, wherein the new RAID stripe comprises a third parity block and third data blocks, wherein at least one of the third data blocks stores a copy of a portion of data from the live RAID stripe, wherein the third parity block is stored on the target SD, and wherein none of the third data blocks is stored on the target SD; and

issue a removal notification when the modified garbage collection operation is completed, wherein the removal notification indicates that the target SD may be removed from the storage array.

14. The system of claim 13, wherein the target SD is identified based on input from a user.

15. The system of claim 13, wherein the target SD is identified based upon an SD service schedule.

16. The system of claim 13, wherein the target SD is identified based upon the target SD exceeding an error event threshold.

17. The system of claim 13, wherein each of the plurality of SDs comprises NAND flash.

18. The system of claim 13, further comprising:

a field programmable gate array (FPGA) configured to calculate the parity value for the RAID stripe.

19. The system of claim 13, wherein the storage controller is configured to track RAID stripe geometry for each of the plurality of live RAID stripes, wherein the RAID stripe geometry for each of the plurality of live RAID stripes is used to perform the modified garbage collection operation.

20. A non-transitory computer readable medium comprising instructions, which when executed by a processor perform a method, the method comprising:

receiving a service notification specifying a target storage device (SD), wherein the target SD is one of plurality of SDs;

after receiving the service notification;

receiving a request to write data to persistent storage, wherein the persistent storage comprises the plurality of SDs;

in response to the request, writing a Redundant Array of Independent Disks (RAID) stripe to the persistent storage wherein the RAID stripe comprises data blocks and a first parity block, wherein at least one of the data blocks comprises a portion of the data, wherein the first parity block comprises a parity value calculated using the data blocks, and wherein the parity block is stored on the target SD and wherein none of the data blocks are stored on the target SD;

performing a modified garbage collection operation, wherein the modified garbage collection operation comprises;

writing a new RAID stripe to a new location in the persistent storage, wherein the new RAID stripe comprises a copy of a first data from a first live RAID stripe and a copy of second data from a second live RAID stripe in the storage array, and wherein the new RAID stripe comprises a second parity block located on the target SD; and

issuing a removal notification when the modified garbage collection operation is completed, wherein the removal notification indicates that the target SD may be removed from the persistent storage.

21. The non-transitory computer readable medium of claim 20, wherein the new RAID stripe further comprises a padding data block.

22. The non-transitory computer readable medium of claim 20, wherein the new RAID stripe further comprises a third parity block, wherein the second parity block comprises a Q parity value and the third parity block comprises a P parity value.

23. The non-transitory computer readable medium of claim 20, wherein the new RAID stripe further comprises a third parity block, wherein the second parity block comprises a P parity value and the third parity block comprises a Q parity value.

24. The non-transitory computer readable medium of claim 20, wherein the first live RAID stripe comprises at least one dead data block.