Reducing a number of storage devices in a storage system that are exhibiting variable I/O response times

• US 10,156,998 B1
• Filed: 01/27/2017
• Issued: 12/18/2018
• Est. Priority Date: 09/15/2010
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Pure Storage, Inc.
• Inventors: Colgrove, John, Hayes, John, Hong, Bo, Wang, Feng, Miller, Ethan, Harmer, Craig
• Primary Examiner(s): Farrokh, Hashem
• Application Number:
  US15/418,035
• Time in Patent Office: 690 Days
• CPC Class Codes: G06F 11/0751 Error or fault detection not based on redundancy power supply failures G06F1/30; network fault management H04L41/06
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID 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 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0617 in relation to availability
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0634 by changing the state or mode of one or more devices
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• 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 system and method for effectively scheduling read and write operations among a plurality of solid-state storage devices. A computer system comprises client computers and data storage arrays coupled to one another via a network. A data storage array utilizes solid-state drives and Flash memory cells for data storage. A storage controller within a data storage array comprises an I/O scheduler. The characteristics of corresponding storage devices are used to schedule I/O requests to the storage devices in order to maintain relatively consistent response times at predicted times. Should a device exhibit an unscheduled behavior which may be indicative of the device being in an unknown state, the scheduler may schedule one or more reactive operations on the device configured to cause the device to enter a known state.

Claims

1. A method of reducing a number of storage devices in a storage system that are exhibiting variable I/O response times, the method comprising:

determining a number of storage devices in a storage system that are servicing high latency operations;

determining whether the number of storage devices in the storage system that are servicing high latency operations exceeds a predetermined target number of storage devices within the device group that may simultaneously service high latency operations; and

responsive to determining that the number of storage devices in the storage system that are servicing high latency operations exceeds the predetermined target number of storage devices within the device group that may simultaneously service high latency operations, halting execution of high latency operations on at least one of the storage devices.

2. The method of claim 1 wherein the predetermined target number of storage devices within the device group that may simultaneously service high latency operations is determined in dependence upon a data redundancy policy.

3. The method of claim 1 further comprising initiating execution of one or more low latency operations on at least one of the storage devices.

4. The method of claim 3 wherein the one or more low latency operations include one or more read requests.

5. The method of claim 1 wherein the high latency operations include at least one write request.

6. The method of claim 1 wherein the high latency operations include at least one cache flush.

7. The method of claim 1 wherein the high latency operations include at least one erase request.

8. A storage system configured for reducing a number of storage devices that are exhibiting variable I/O response times, the storage system including a computer memory and a computer processor, the computer processor including computer program instructions that, when executed by the computer processor, cause the storage system to carry out the steps of:

determining a number of storage devices in a storage system that are servicing high latency operations;

determining whether the number of storage devices in the storage system that are servicing high latency operations exceeds a predetermined target number of storage devices within the device group that may simultaneously service high latency operations; and

responsive to determining that the number of storage devices in the storage system that are servicing high latency operations exceeds the predetermined target number of storage devices within the device group that may simultaneously service high latency operations, halting execution of high latency operations on at least one of the storage devices.

9. The storage system of claim 8 wherein the predetermined target number of storage devices within the device group that may simultaneously service high latency operations is determined in dependence upon a data redundancy policy.

10. The storage system of claim 8 further comprising computer program instructions that, when executed by the computer processor, cause the storage system to carry out the step of initiating execution of one or more low latency operations on at least one of the storage devices.

11. The storage system of claim 10 wherein the one or more low latency operations include one or more read requests.

12. The storage system of claim 8 wherein the high latency operations include at least one write request.

13. The storage system of claim 8 wherein the high latency operations include at least one cache flush.

14. The storage system of claim 8 wherein the high latency operations include at least one erase request.

15. An apparatus for reducing a number of storage devices in a storage system that are exhibiting variable I/O response times, the apparatus including a computer memory and a computer processor, the computer processor including computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

determining a number of storage devices in a storage system that are servicing high latency operations;

determining whether the number of storage devices in the storage system that are servicing high latency operations exceeds a predetermined target number of storage devices within the device group that may simultaneously service high latency operations; and

responsive to determining that the number of storage devices in the storage system that are servicing high latency operations exceeds the predetermined target number of storage devices within the device group that may simultaneously service high latency operations, halting execution of high latency operations on at least one of the storage devices.

16. The apparatus of claim 15 wherein the predetermined target number of storage devices within the device group that may simultaneously service high latency operations is determined in dependence upon a data redundancy policy.

17. The apparatus of claim 15 further comprising computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the step of initiating execution of one or more low latency operations on at least one of the storage devices.

18. The apparatus of claim 17 wherein the one or more low latency operations include one or more read requests.

19. The apparatus of claim 17 wherein the high latency operations include at least one write request.

20. The apparatus of claim 17 wherein the high latency operations include at least one cache flush.