Performing discard commands on RAID storage devices

• US 9,009,388 B2
• Filed: 11/30/2010
• Issued: 04/14/2015
• 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: Snitzer, Michael A., Patoka, Mikul
• Primary Examiner(s): Bradley, Matthew
• Assistant Examiner(s): TSUI, DANIEL D
• Application Number:
  US12/956,250
• Publication Number:
  US 20120137064A1
• Time in Patent Office: 1,596 Days
• Field of Search: None
• US Class Current: 711/103
• 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 comprising:

receiving, by a processing device, a request to free a range of logical sectors that is mapped to a plurality of storage devices organized as Redundant Array of Independent Disks (RAID), each storage device partitioned into a plurality of partitions to store a plurality of physical sectors;

for each storage device, identifying a first physical sector number corresponding to a first logical sector having a lowest number greater or equal than a starting logical sector number of the range of logical sectors;

identifying a second physical sector number corresponding to a second logical sector having a lowest number greater or equal than an ending logical sector number of the range of logical sectors; and

issuing a command to free a range of physical sectors identified by the first physical sector number and the second physical sector number;

wherein identifying a physical sector number on a current device comprises determining a first integer corresponding to a specified logical sector number and a second integer corresponding to the specified logical sector number, rounding down the first integer to a partition boundary responsive to determining that the second integer exceeds an ordinal number of the current device, and rounding down the first integer incremented by one to a partition boundary responsive to determining that the second integer does not exceed an ordinal number of the current device.

2. The method of claim 1, wherein issuing the command comprises:

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

3. The method of claim 1, wherein issuing the command to free a physical sector in a parity group is performed if all physical sectors in the parity group are to be discarded.

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

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

6. The method of claim 1, wherein identifying the first integer comprises adding, to the specified logical sector number modulo a partition size, an integer quotient of the specified logical sector number and a number of storage devices.

7. The method of claim 1, wherein identifying the second integer comprises determining a quotient of the specified logical sector number and a partition size modulo a number of storage devices.

8. The method of claim 1, wherein the rounding down comprises applying bit mask.

9. A system comprising:

a plurality of storage devices organized as a Redundant Array of Independent Disks (RAID), each storage device partitioned into a plurality of partitions to store a plurality of physical sectors; and

a processing device coupled to the storage devices, the processing device to;

receive a request to free a range of logical sectors that is mapped to the storage devices;

identify, for each storage device, a first physical sector number corresponding to a logical sector having a lowest number greater or equal than a starting logical sector number of the range of logical sectors;

identify, for each storage device, a second physical sector number corresponding to a logical sector having a lowest number greater or equal than an ending logical sector number of the range of logical sectors; and

issue, for each storage device, a command to free a range of physical sectors identified by the first physical sector number and the second physical sector number;

wherein identifying a physical sector number on a current device comprises determining a first integer corresponding to a specified logical sector number and a second integer corresponding to the specified logical sector number, rounding down the first integer to a partition boundary responsive to determining that the second integer exceeds an ordinal number of the current device, and rounding down the first integer incremented by one to a partition boundary responsive to determining that the second integer does not exceed an ordinal number of the current device.

10. The system of claim 9, further comprising:

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

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

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

13. The system of claim 9, wherein identifying the first integer comprises adding, to the specified logical sector number modulo a partition size, an integer quotient of the specified logical sector number and a number of storage devices.

14. The system of claim 9, wherein identifying the second integer comprises determining a quotient of the specified logical sector number and a partition size modulo a number of storage devices.

15. A computer readable non-transitory storage medium including instructions that, when executed by a processing device, cause the processing device to perform operations comprising:

receiving, by the processing device, a request to free a range of logical sectors that is mapped to a plurality of storage devices organized as Redundant Array of Independent Disks (RAID), each storage device partitioned into a plurality of partitions to store a plurality of physical sectors;

for each storage device, identifying a first physical sector number corresponding to a logical sector having a lowest number greater or equal than a starting logical sector number of the range of logical sectors;

identifying a second physical sector number corresponding to a logical sector having a lowest number greater or equal than an ending logical sector number of the range of logical sectors; and

issuing a command to free a range of physical sectors identified by the first physical sector number and the second physical sector number;

wherein identifying a physical sector number on a current device comprises determining a first integer corresponding to a specified logical sector number and a second integer corresponding to the specified logical sector number, rounding down the first integer to a partition boundary responsive to determining that the second integer exceeds an ordinal number of the current device, and rounding down the first integer incremented by one to a partition boundary responsive to determining that the second integer does not exceed an ordinal number of the current device.

16. The computer readable storage medium of claim 15, wherein issuing the command comprises:

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

17. The computer readable storage medium of claim 15, wherein issuing the command to free a physical sector in a parity group is performed if all physical sectors in the parity group are to be discarded.

18. The computer readable storage medium of claim 15, wherein the storage devices are organized as RAID-0, RAID-4, RAID-5 or RAID-6.

19. The computer readable non-transitory storage medium of claim 15, wherein identifying the first integer comprises adding, to the specified logical sector number modulo a partition size, an integer quotient of the specified logical sector number and a number of storage devices.

20. The computer readable non-transitory storage medium of claim 15, wherein identifying the second integer comprises determining a quotient of the specified logical sector number and a partition size modulo a number of storage devices.