Method and system for service-aware parity placement in a storage system
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.
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 a plurality of SDs in persistent storage;
after receiving the service notification:
performing a modified garbage collection operation, wherein the modified garbage collection operation comprises:
identifying a live Redundant Array of Independent Disks (RAID) stripe in the persistent storage, wherein the live RAID stripe comprises first data blocks and a first parity block;
making a determination that at least one selected from a group consisting of a data block of the first data blocks and the first parity block is a dead block and that at least one of the first data blocks is a live block;
writing a first RAID stripe to a new location in the persistent storage, wherein the first RAID stripe comprises a second parity block and second data blocks, wherein one of the second data blocks stores a copy of the live block, wherein the second parity block is stored on the target SD, wherein none of the second data blocks are stored on the target SD, and wherein content of the dead block is not stored in any of the second data blocks; 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 method further comprises:
after receiving the service notification and prior the issuance of the removal notification:
receiving a request to write data to the persistent storage;
in response to the request, writing a second RAID stripe to the persistent storage, wherein the second RAID stripe comprises third data blocks and a third parity block, wherein at least one of the third data blocks comprises a portion of the data, wherein the third parity block comprises a parity value calculated using the third data blocks, and wherein the third parity block is stored on the target SD, and wherein none of the third data blocks are stored on the target SD.
3. 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.
4. 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, 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 first RAID stripe is associated with a second RAID stripe geometry, wherein the second RAID stripe geometry is different than the RAID stripe geometry.
6. The non-transitory computer readable medium of claim 1 , wherein the first RAID stripe further comprises a third parity value, wherein the second parity value is a Q parity value, wherein the third parity value is a P parity value.
7. The non-transitory computer readable medium of claim 1 , wherein the second parity block comprises at least one selected from a group consisting of a P parity value and a Q parity value.
8. The non-transitory computer readable medium of claim 1 , wherein at least one of the plurality of SDs is a solid state memory device.
9. 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.
10. The non-transitory computer readable medium of claim 1 , wherein the first RAID stripe further comprises a padding data block.
11. 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:
receive a service notification specifying a target storage device (SD), wherein the target SD is one of the plurality of SDs;
after receiving the service notification:
perform a modified garbage collection operation, wherein the modified garbage collection operation comprises:
identifying a live Redundant Array of Independent Disks (RAID) stripe in the persistent storage, wherein the live RAID stripe comprises first data blocks and a first parity block;
making a determination that at least one selected from a group consisting of a data block of the first data blocks and the first parity block is a dead block and that at least one of the first data blocks is a live block;
writing a first RAID stripe to a new location in the persistent storage, wherein the first RAID stripe comprises a second parity block and second data blocks, wherein one of the second data blocks stores a copy of the live block, wherein the second parity block is stored on the target SD, wherein none of the second data blocks are stored on the target SD, and wherein content of the dead block is not stored in any of the second data blocks; 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 persistent storage.
12. The system of claim 11 , wherein the storage controller is further configured to:
after receiving the service notification and prior the issuance of the removal notification:
receive a request to write data to the persistent storage;
in response to the request, write a second RAID stripe to the persistent storage, wherein the third RAID stripe comprises third data blocks and a third parity block, wherein at least one of the third data blocks comprises a portion of the data, wherein the third parity block comprises a parity value calculated using the third data blocks, and wherein the third parity block is stored on the target SD, and wherein none of the third data blocks are stored on the target SD.
13. The system of claim 11 , wherein the target SD is identified based on input from a user.
14. The system of claim 11 , wherein the target SD is identified based upon an SD service schedule.
15. The system of claim 11 , wherein the target SD is identified based upon the target SD exceeding an error event threshold.
16. The system of claim 11 , wherein each of the plurality of SDs comprises NAND flash.
17. The system of claim 11 , further comprising:
a field programmable gate array (FPGA) configured to calculate the second parity value for the first RAID stripe.
18. The system of claim 11 , wherein the storage controller is further 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.
19. A method for managing persistent storage, comprising:
receiving a service notification specifying a target storage device (SD), wherein the target SD is one of a plurality of SDs in the persistent storage;
after receiving the service notification:
performing a modified garbage collection operation, wherein the modified garbage collection operation comprises:
identifying a live Redundant Array of Independent Disks (RAID) stripe in the persistent storage, wherein the live RAID stripe comprises first data blocks and a first parity block;
making a determination that at least one selected from a group consisting of a data block of the first data blocks and the first parity block is a dead block and that at least one of the first data blocks is a live block;
writing a first RAID stripe to a new location in the persistent storage, wherein the first RAID stripe comprises a second parity block and second data blocks, wherein one of the second data blocks stores a copy of the live block, wherein the second parity block is stored on the target SD, wherein none of the second data blocks are stored on the target SD, and wherein content of the dead block is not stored in any of the second data blocks; 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.
20. The method of claim 19 , further comprising:
after receiving the service notification and prior the issuance of the removal notification:
receiving a request to write data to the persistent storage;
in response to the request, writing a second RAID stripe to the persistent storage, wherein the second RAID stripe comprises third data blocks and a third parity block, wherein at least one of the third data blocks comprises a portion of the data, wherein the third parity block comprises a parity value calculated using the third data blocks, and wherein the third parity block is stored on the target SD, and wherein none of the third data blocks are stored on the target SD.