Implementing I/O locks in storage systems with reduced memory and performance costs

• US 7,647,443 B1
• Filed: 04/11/2008
• Issued: 01/12/2010
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: AmZetta Technologies, LLC (American Megatrends International, LLC)
• Original Assignee: American Megatrends Incorporated
• Inventors: Chatterjee, Paresh, Narayanan, Ajit, Enoch, Sharon, Ranganathan, Loganathan
• Primary Examiner(s): Stiglic; Ryan M
• Application Number:
  US12/101,240
• Time in Patent Office: 641 Days
• Field of Search: 710/200
• US Class Current: 710/200
• CPC Class Codes: G06F 3/0622 in relation to access
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

Technologies are described for implementing locks to control I/O operations in a storage system. The lock implementations can have reduced resource requirements for memory and processing. Through the utilization of the technologies and concepts presented herein, an I/O process preparing to acquire a write lock can advertise its need for the lock for a pre-determined time before the lock is granted. The time period for advertisement can be specified so that all I/O operations that were initiated before the advertisement are guaranteed to have completed by the time the advertisement period is over. As such, a lock controller may only need to track outstanding I/Os that begin once the advertisement starts. This can reduce the typical requirement to maintain and process a lock structure for every unit of storage in the system at all times.

Claims

1. A method for managing input/output locks in a data storage system, the method comprising:

receiving a write lock request related to a data storage entity;

operating a timer for a fixed duration of time in response to receiving the write lock request;

granting read lock requests received during the fixed duration of time; and

granting the write lock request after the fixed duration of time and after verifying release of each of the read locks granted during the fixed duration of time.

2. The method of claim 1, further comprising queuing read lock requests received after the fixed duration of time and before a release of the granted write lock.

3. The method of claim 2, further comprising granting each queued read lock request in response to the release of the granted write lock.

4. The method of claim 1, wherein operating the timer comprises initializing the timer to a duration sufficient to allow the completion of each of a plurality of prior read lock requests.

5. The method of claim 1, wherein operating the timer comprises periodically decrementing a timer value.

6. The method of claim 1, further comprising creating a lock data structure in response to receiving the write lock request;

and destroying the lock data structure in response to a release of the granted write lock.

7. The method of claim 6, further comprising granting untracked read locks when the lock data structure is not present.

8. A computer storage medium having computer-executable instructions stored thereon which, when executed by a computer system, cause the computer system to:

receive a write lock request related to a data storage entity;

operate a timer for a fixed duration of time in response to receiving the write lock request;

grant read lock requests received during the fixed duration of time; and

grant the write lock request after the fixed duration of time and after verifying release of each of the read locks granted during the fixed duration of time.

9. The computer storage medium of claim 8, further causing the computer system to queue read lock requests received after the fixed duration of time and before a release of the granted write lock.

10. The computer storage medium of claim 9, further causing the computer system to grant each queued read lock request in response to the release of the granted write lock.

11. The computer storage medium of claim 8, wherein operating the timer comprises initializing the timer to a duration sufficient to allow the completion of each of a plurality of prior read lock requests.

12. The computer storage medium of claim 8, wherein operating the timer comprises periodically decrementing a timer value.

13. The computer storage medium of claim 8, further causing the computer system to create a lock data structure in response to receiving the write lock request;

and destroy the lock data structure in response to the release of the granted write lock.

14. A data storage system comprising:

a storage subsystem;

a physical storage device associated with the storage subsystem; and

one or more lock controller modules operable to cause the storage subsystem to;

receive a write lock request related to a data storage entity;

operate a timer for a fixed duration of time in response to receiving the write lock request;

grant read lock requests received during the fixed duration of time; and

grant the write lock request after the fixed duration of time and after verifying release of each of the read locks granted during the fixed duration of time.

15. The data storage system of claim 14, wherein the lock controller modules are further operable to cause the storage subsystem to queue read lock requests received after the fixed duration of time and before a release of the granted write lock.

16. The data storage system of claim 15, wherein the lock controller modules are further operable to cause the storage subsystem to grant each queued read lock request in response to the release of the granted write lock.

17. The data storage system of claim 14, wherein operating the timer comprises initializing the timer to a duration sufficient to allow the completion of each of a plurality of prior read lock requests.

18. The data storage system of claim 14, wherein operating the timer comprises periodically decrementing a timer value.

19. The data storage system of claim 14, wherein the lock controller modules are further operable to cause the storage subsystem to create a lock data structure in response to receiving the write lock request;

and destroying the lock data structure in response to the release of the granted write lock.

20. The data storage system of claim 19, wherein the lock controller modules are further operable to cause the storage subsystem to grant untracked read locks when the lock data structure is not present.