EFFICIENT DISCARD COMMANDS ON RAID STORAGE DEVICES

• US 20120137064A1
• Filed: 11/30/2010
• Published: 05/31/2012
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: Patocka, Mikulás, Snitzer, Michael A.
• Granted Patent: US 9,009,388 B2
• Time in Patent Office: Days
• US Class Current: 711/114
• CPC Class Codes: G06F 12/0238 Memory management in non-volatile memory, e.g. resistive RAM or ferroelectric memory
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method and system for efficiently freeing storage in a Redundant Array of Independent Disks (RAID) system. A computer system is coupled to storage devices that are organized as a RAID with block-level striping. Each storage device is partitioned into multiple physical sectors. The computer system receives a request to free a contiguous range of logical sectors that are mapped to the storage devices. In response, the computer system issues, for each storage device, a discard command to free contiguous physical sectors in the storage device that correspond to non-contiguous logical sectors.

Claims

1. A method, implemented by a computer system programmed to perform the following, comprising:

receiving, by the computer system, a request to free a contiguous range of logical sectors that are mapped to storage devices organized as Redundant Array of Independent Disks (RAID) with block-level striping, each storage device being partitioned into a plurality of physical sectors;

for each storage device, issuing, by the computer system, a discard command to free contiguous physical sectors in the storage device that correspond to non-contiguous logical sectors.

2. The method of claim 1, wherein issuing a discard command further comprises:

calculating a range of the contiguous physical sectors using two divisions and two modulo operations; and

issuing a single discard command indicating the range of the contiguous physical sectors.

3. The method of claim 1, wherein the RAID uses parity, the method further comprising:

issuing the discard command to each device indicating a same range of the contiguous physical sectors.

4. The method of claim 1, wherein the RAID does not use parity and the contiguous range of logical sectors are identified by a starting logical sector number and an ending logical sector number, the method further comprising:

calculating a first physical sector number based on a given storage device number and the starting logical sector number;

calculating a second physical sector number based on the given storage device number and the ending logical sector number; and

calculating a range of the contiguous physical sectors for the given storage device based on the first physical sector number and the second physical sector number.

5. The method of claim 1, wherein the RAID uses parity, the method comprising:

issuing the discard command to free a physical sector in a parity group only if all of associated physical sectors in the parity group are to be discarded.

6. The method of claim 1, wherein the RAID uses parity, and the contiguous range of logical sectors are identified by a starting logical sector number and an ending logical sector number, the method further comprising:

calculating a first physical sector number and a first storage device number based on the starting logical sector number;

calculating a second physical sector number and a second storage device number based on the ending logical sector number; and

calculating a same range of the contiguous physical sectors for all of the storage devices based on the first physical sector number, the second physical sector number, the first storage device number and the second storage device number.

7. The method of claim 1, wherein the RAM comprises solid state devices (SSDs).

8. The method of claim 1, wherein the storage devices are organized as RAID-0, RAID-4, RAID-5 or RAID-6.

9. A system comprising:

a plurality of storage devices organized as a Redundant Array of Independent Disks (RAID) with block-level striping, each storage device partitioned into a plurality of physical sectors; and

a computer system coupled to the storage devices, the computer system to receive a request to free a contiguous range of logical sectors that are mapped to the storage devices, and to issue, for each storage device, a discard command to free contiguous physical sectors in the storage device that correspond to non-contiguous logical sectors.

10. The system of claim 9, further comprising:

an arithmetic module to calculate a range of the contiguous physical sectors with two divisions and two modulo operations.

11. The system of claim 9, wherein the RAID uses parity, the system further comprises:

a RAID driver odule to free a physical sector in a parity group only if all of associated physical sectors in the parity group are to be discarded.

12. The system of claim 9, wherein the RAID comprises solid state devices (SSDs).

13. The system of claim 9, wherein the storage devices are organized as RAID-0, RAID-4, RAID-5 or RAID-6.

14. A computer readable storage medium ncluding instructions that, when executed by a processing system, cause the processing system to perform a method comprising:

receiving a request to free a contiguous range of logical sectors that are mapped to storage devices organized as Redundant Array of Independent Disks (RAID) with block-level striping, each storage device being partitioned into a plurality of physical sectors;

for each storage device, issuing a discard command to free contiguous physical sectors in the storage device that correspond to non-contiguous logical sectors.

15. The computer readable storage medium of claim 14, wherein issuing a discard command further comprises:

calculating a range of the contiguous physical sectors using two divisions and two modulo operations; and

issuing a single discard command indicating the range of the contiguous physical sectors.

16. The computer readable storage medium of claim 14, wherein the RAID uses parity, the method further comprising:

issuing the discard command to each device indicating a same range of the contiguous physical sectors.

17. The computer readable storage medium of claim 14, wherein the RAID does not use parity and the contiguous range of logical sectors are identified by a starting logical sector number and an ending logical sector number, the method further comprising:

calculating a first physical sector number based on a given storage device number and the starting logical sector number;

calculating a second physical sector number based on the given storage device number and the ending logical sector number; and

calculating a range of the contiguous physical sectors for the given storage device based on the first physical sector number and the second physical sector number.

18. The computer readable storage medium of claim 14, wherein the RAID uses parity, the method comprising:

issuing the discard command to free a physical sector in a parity group only if all of associated physical sectors in the parity group are to be discarded.

19. The computer readable storage medium of claim 14, wherein the RAID uses one or more parities, and the contiguous range of logical sectors are identified by a starting logical sector number and an ending logical sector number, the method further comprising:

calculating a first physical sector number and a first storage device number based on the starting logical sector number;

calculating a second physical sector number and a second storage device number based on the ending logical sector number; and

calculating a same range of the contiguous physical sectors for all of the storage devices based on the first physical sector number, the second physical sector number, the first storage device number and the second storage device number.

20. The computer readable storage medium of claim 14, wherein the storage devices are organized as RAID-0, RAID-4, RAID-5 or RAID-6.