Scheduling of I/O writes in a storage environment

• US 9,423,967 B2
• Filed: 05/18/2015
• Issued: 08/23/2016
• 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): Gu, Shawn X
• Application Number:
  US14/715,552
• Publication Number:
  US 20150254004A1
• Time in Patent Office: 463 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0238 Memory management in non-volatile memory, e.g. resistive RAM or ferroelectric memory
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 12/0802 Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
• CPC Class Codes: G06F 12/0891 using clearing, invalidating or resetting means
• CPC Class Codes: G06F 2212/60 Details of cache memory
• CPC Class Codes: G06F 3/06 Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers
• 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 3/0629 Configuration or reconfiguration of storage systems
• CPC Class Codes: G06F 3/0653 Monitoring storage devices or systems
• 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 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0683 Plurality of storage devices
• 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 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 data storage controller is configured to receive requests targeted to the data storage medium, said requests including a first type of operation and a second type of operation. The controller is further configured to schedule requests of the first type for immediate processing by said plurality of storage devices, and queue requests of the second type for later processing by the plurality of storage devices. Operations of the first type may correspond to operations with an expected relatively low latency, and operations of the second type may correspond to operations with an expected relatively high latency.

Claims

1. A computer system comprising:

a data storage medium comprising a plurality of storage devices configured to store data;

and a data storage controller coupled to the data storage medium;

wherein the data storage controller is configured to;

cease processing requests corresponding to a first type of operation on a first storage device;

queue a plurality of requests of a second type of operation;

schedule requests of the second type for immediate processing by the first storage device; and

in response to detecting a second storage device of the plurality of storage devices is exhibiting a relatively long response latency, discontinue processing the requests corresponding to the second type of operation by the first storage device.

2. The computer system as recited in claim 1, wherein operations of the first type correspond to operations with an expected relatively low latency, and operations of the second type correspond to operations with an expected relatively high latency.

3. The computer system as recited in claim 2, wherein operations of the first type correspond to read requests, and operations of the second type correspond to write requests, cache flushes, or trim operations.

4. The computer system as recited in claim 1, wherein said plurality of storage devices are solid state storage devices, and wherein each of said solid state storage devices processes read requests with a relatively low latency, and processes write requests with a relatively high latency.

5. The computer system as recited in claim 1, wherein the plurality of requests corresponding to the second type of operation correspond to write requests, and wherein the storage controller is configured to automatically schedule a dummy read to a given device to follow the write requests.

6. The computer system as recited in claim 1, wherein the plurality of requests corresponding to the second type of operation correspond to write requests, and wherein the storage controller is configured to stream said write requests as a plurality of discrete units of data for processing, the storage controller being able to stop said streaming after any of said units.

7. The computer system as recited in claim 1, wherein the storage controller is configured to stop processing requests corresponding to the first type immediately and begin processing queued requests corresponding to the second type in response to detecting a given condition.

8. The computer system as recited in claim 7, wherein said condition comprises at least one of:

a particular number of requests of the second type have been queued, a period of time has elapsed since requests of the second type were processed, and no new requests have been received for a given period of time.

9. A method for use in a computing system, the method comprising:

cease processing requests corresponding to a first type of operation on a first storage device;

queue a plurality of requests of a second type of operation;

schedule requests of the second type for immediate processing by the first storage device; and

in response to detecting a second storage device of the plurality of storage devices is exhibiting a relatively long response latency, discontinue processing the requests corresponding to the second type of operation by the first storage device.

10. The method as recited in claim 9, wherein operations of the first type correspond to operations with an expected relatively low latency, and operations of the second type correspond to operations with an expected relatively high latency.

11. The method as recited in claim 10, wherein operations of the first type correspond to read requests, and operations of the second type correspond to write requests, cache flushes, or trim operations.

12. The method as recited in claim 9, wherein said plurality of storage devices are solid state storage devices, and wherein each of said solid state storage devices processes read requests with a relatively low latency, and processes write requests with a relatively high latency.

13. The method as recited in claim 9, wherein the plurality of requests corresponding to the second type of operation correspond to write requests, and wherein the method comprises automatically scheduling a dummy read to a given device to follow the write requests.

14. The method as recited in claim 9, wherein the plurality of requests corresponding to the second type of operation correspond to write requests, and wherein the method comprises streaming said write requests as a plurality of discrete units of data for processing, the method being able to stop said streaming after any of said units.

15. A non-transitory computer readable storage medium comprising program instructions, wherein when executed by a processing device, the program instructions are operable to:

cease processing requests corresponding to a first type of operation on a first storage device;

queue a plurality of requests of a second type of operation;

schedule requests of the second type for immediate processing by the first storage device; and

in response to detecting a second storage device of the plurality of storage devices is exhibiting a relatively long response latency, discontinue processing the requests corresponding to the second type of operation by the first storage device.

16. The computer readable medium as recited in claim 15, wherein operations of the first type correspond to operations with an expected relatively low latency, and operations of the second type correspond to operations with an expected relatively high latency.