Maintaining a target number of storage devices for variable I/O response times in a storage system

• US 10,228,865 B1
• Filed: 04/30/2018
• Issued: 03/12/2019
• 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:
  US15/967,408
• Time in Patent Office: 316 Days
• Field of Search: 711114
• 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 maintaining a target number of storage devices for variable I/O response times in a storage system, the method comprising:

setting a target number of storage devices in a device group of a storage system to concurrently exhibit variable I/O response times;

detecting one or more conditions in the device group; and

changing the target number in response to detecting one or more conditions in the device group.

2. The method of claim 1 further comprising determining in the device group, a number of storage devices that are concurrently exhibiting variable I/O response times.

3. The method of claim 2 further comprising:

determining whether the number of storage devices that are concurrently exhibiting variable I/O response times is greater than the target number;

if the number of storage devices that are concurrently exhibiting variable I/O response times is greater than the target number, scheduling requests to the device group to reduce the number of storage devices that are concurrently exhibiting variable I/O response times; and

if the number of storage devices that are concurrently exhibiting variable I/O response times is not greater than the target number, scheduling requests to improve performance of the device group.

4. The method of claim 1, wherein detecting one or more conditions in the device group include determining that a number of pending write requests for a given device in the device group exceeds a waiting threshold.

5. The method of claim 1, wherein detecting one or more conditions in the device group include detecting a given number of high-priority write requests in the device group.

6. The method of claim 1, wherein exhibiting variable I/O response times includes executing high-latency operations.

7. A storage system configured for maintaining a target number of storage devices for variable I/O response times in a storage system, 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 to 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 to simultaneously service high latency operations, halting execution of high latency operations on at least one of the storage devices.

8. The storage system of claim 7 further comprising computer program instructions that, when executed by the computer processor, cause the storage system to carry out the steps of determining in the device group, a number of storage devices that are concurrently exhibiting variable I/O response times.

9. 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 steps of:

determining whether the number of storage devices that are concurrently exhibiting variable I/O response times is greater than the target number;

if the number of storage devices that are concurrently exhibiting variable I/O response times is greater than the target number, scheduling requests to the device group to reduce the number of storage devices that are concurrently exhibiting variable I/O response times; and

if the number of storage devices that are concurrently exhibiting variable I/O response times is not greater than the target number, scheduling requests to improve performance of the device group.

10. The storage system of claim 7, wherein detecting one or more conditions in the device group include determining that a number of pending write requests for a given device in the device group exceeds a waiting threshold.

11. The storage system of claim 7, wherein detecting one or more conditions in the device group include detecting a given number of high-priority write requests in the device group.

12. The storage system of claim 7, wherein exhibiting variable I/O response times includes executing high-latency operations.

13. An apparatus for maintaining a target number of storage devices for variable I/O response times in a storage system, 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 to 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 to simultaneously service high latency operations, halting execution of high latency operations on at least one of the storage devices.

14. The apparatus of claim 13 further comprising computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of determining in the device group, a number of storage devices that are concurrently exhibiting variable I/O response times.

15. The apparatus of claim 14 further comprising computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

determining whether the number of storage devices that are concurrently exhibiting variable I/O response times is greater than the target number;

if the number of storage devices that are concurrently exhibiting variable I/O response times is greater than the target number, scheduling requests to the device group to reduce the number of storage devices that are concurrently exhibiting variable I/O response times; and

if the number of storage devices that are concurrently exhibiting variable I/O response times is not greater than the target number, scheduling requests to improve performance of the device group.

16. The apparatus of claim 13, wherein detecting one or more conditions in the device group include determining that a number of pending write requests for a given device in the device group exceeds a waiting threshold.

17. The apparatus of claim 13, wherein detecting one or more conditions in the device group include detecting a given number of high-priority write requests in the device group.

18. The apparatus of claim 13, wherein exhibiting variable I/O response times includes executing high-latency operations.