Method and apparatus for decomposing I/O tasks in a RAID system

• US 8,621,465 B2
• Filed: 03/15/2011
• Issued: 12/31/2013
• Est. Priority Date: 03/21/2002
• Status: Expired due to Term

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Leong, James, Sundaram, Rajesh, Doucette, Douglas P., Schoenthal, Scott, Strange, Stephen H., Viswanathan, Srinivasan
• Primary Examiner(s): Wu, Qing
• Application Number:
  US13/048,513
• Publication Number:
  US 20110191780A1
• Time in Patent Office: 1,022 Days
• Field of Search: None
• US Class Current: 718/100
• CPC Class Codes: G06F 11/2087 with a common controller
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0655 Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues

Abstract

A data access request to a file system is decomposed into a plurality of lower-level I/O tasks. A logical combination of physical storage components is represented as a hierarchical set of objects. A parent I/O task is generated from a first object in response to the data access request. A child I/O task is generated from a second object to implement a portion of the parent I/O task. The parent I/O task is suspended until the child I/O task completes. The child I/O task is executed in response to an occurrence of an event that a resource required by the child I/O task is available. The parent I/O task is resumed upon an event indicating completion of the child I/O task. Scheduling of any child I/O task is not conditional on execution of the parent I/O task, and a state diagram regulates the child I/O tasks.

Claims

1. A method for processing data access requests at a storage system, comprising:

representing components of a storage operating system of the storage system as a set of objects, the storage operating system executed by a processor of the storage system;

receiving a data access request at the storage system directed to the set of objects;

decomposing the data access request to generate a parent I/O task and a child I/O task;

assigning the parent I/O task to a first object in the set of objects;

assigning the child I/O task to a second object in the set of objects;

scheduling the child I/O task for execution independently from execution of the parent I/O task; and

executing the child I/O task assigned to the second object.

2. The method of claim 1 wherein the components of the storage operating system comprise components of a RAID system.

3. The method of claim 1 further comprising assigning a hierarchical order to the parent I/O task and the child I/O task.

4. The method of claim 1 wherein the set of objects comprise at least one of a volume object, a mirror object, and a plex object.

5. The method of claim 1 further comprising, in response to generating the child I/O task, dynamically allocating a resource for the child I/O task.

6. The method of claim 5 further comprising suspending the child I/O task if the resource is not available.

7. The method of claim 1 further comprising changing the parent I/O task from a first state of a plurality of states to a second state of the plurality of states in response to an occurrence of an event.

8. The method of claim 7 wherein the plurality of states comprises at least one of a perform I/O task state, a child I/O task pending state, an XOR task pending state, an I/O task finished state, and an I/O task suspended state.

9. The method of claim 7 wherein the event comprises at least one of a storage device I/O completion, a RAID group I/O completion, mirror I/O completion, plex I/O completion, volume I/O completion, and a request from a RAID client.

10. The method of claim 1 wherein the parent I/O task comprises at least one of a storage device read, a storage device write, a volume write, a volume read, a mirror write, a mirror read, a plex write, a plex read, a group read, an array write, a parity reconstruction of a RAID group, a stripe parity reconstruction and a mirror verification.

11. A system to process data access requests at a storage system, comprising:

a processor of the storage system configured to execute a storage operating system, the storage operating system configured to represent components of the storage operating system as a set of objects;

the storage operating system further configured to receive a data access request directed to the set of objects;

the storage operating system further configured to decompose the data access request to generate a parent I/O task and a child I/O task;

the storage operating system further configured to assign the parent I/O task to a first object in the set of objects;

the storage operating system further configured to assign the child I/O task to a second object in the set of objects;

the storage operating system further configured to schedule the child I/O task for execution independently from execution of the parent I/O task; and

the storage operating system further configured to execute the child I/O task assigned to the second object.

12. The system of claim 11 wherein the components of the storage operating system comprise components of a RAID system.

13. The system of claim 11 wherein the storage operating system is further configured to assign a hierarchical order to the parent I/O task and the child I/O task.

14. The system of claim 11 wherein the set of objects comprise at least one of a volume object, a mirror object, and a plex object.

15. The system of claim 11 wherein the storage operating system is further configured to dynamically allocating a resource for the child I/O task in response to generating the child I/O task.

16. The system of claim 15 wherein the storage operating system is further configured to suspend the child I/O task if the resource is not available.

17. The system of claim 11 wherein the storage operating system is further configured to change the parent I/O task from a first state of a plurality of states to a second state of the plurality of states in response to an occurrence of an event.

18. The system of claim 17 wherein the plurality of states comprises at least one of a perform I/O task state, a child I/O task pending state, an XOR task pending state, an I/O task finished state, and an I/O task suspended state.

19. The system of claim 17 wherein the event comprises at least one of a storage device I/O completion, a RAID group I/O completion, mirror I/O completion, plex I/O completion, volume I/O completion, and a request from a RAID client.

20. The system of claim 11 wherein the parent I/O task comprises at least one of a storage device read, a storage device write, a volume write, a volume read, a mirror write, a mirror read, a plex write, a plex read, a group read, an array write, a parity reconstruction of a RAID group, a stripe parity reconstruction and a mirror verification.

21. A non-transitory computer-readable storage medium containing executable program instructions for execution by a processor, the computer-readable storage medium comprising:

program instructions that represent components of a storage operating system of the storage system as a set of objects, the storage operating system executed by a processor of the storage system;

program instructions that receive a data access request at the storage system directed to the set of objects;

program instructions that decompose the data access request to generate a parent I/O task and a child I/O task;

program instructions that assign the parent I/O task to a first object in the set of objects;

program instructions that assign the child I/O task to a second object in the set of objects;

program instructions that schedule the child I/O task for execution independently from execution of the parent I/O task; and

program instructions that execute the child I/O task assigned to the second object.

22. A system configured to process data access requests at a storage system, comprising:

means for representing components of a storage operating system of the storage system as a set of objects, the storage operating system executed by a processor of the storage system;

means for receiving a data access request at the storage system directed to the set of objects;

means for decomposing the data access request to generate a parent I/O task and a child I/O task;

means for assigning the parent I/O task to a first object in the set of objects;

means for assigning the child I/O task to a second object in the set of objects;

means for scheduling the child I/O task for execution independently from execution of the parent I/O task; and

means for executing the child I/O task assigned to the second object.