Throttling in storage systems

• US 20040148484A1
• Filed: 01/23/2003
• Published: 07/29/2004
• Est. Priority Date: 01/23/2003
• Status: Active Grant

• Current Assignee: Ceradyne, Inc. (3M Company), Google LLC (Alphabet Inc.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Watanabe, Naoki, Kishiro, Shigeru
• Granted Patent: US 7,127,568 B2
• Time in Patent Office: Days
• US Class Current: 711/170
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 3/061 Improving I/O performance
• 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 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method is provided for improving the performance of copy operations in storage systems. The method includes storing a measure of relative availability of storage system resources, detecting operations when sequential portions of a storage media are to be accessed for writing of information, and when the measure of relative availability of system resources drops to a specified extent, introducing a wait into the operation in which sequential portions of a storage media are to be accessed for writing of information. In another implementation, a method is provided for controlling writing of data in a storage system in which a step is performed of analyzing a requested write operation to determine if the requested write operation calls for a sequential task or a random task. If the requested write operation is a sequential task, information about it is stored in a task management table. the table is used to determine if throttling is needed to carry out the requested write operation, and invokes throttling if it is needed.

Claims

1. A method of improving the performance of copy operations in storage systems having resources, the method comprising:

storing a measure of relative availability of storage system resources;

detecting operations when sequential portions of a storage media are to be accessed for writing of information; and

when the measure of relative availability of system resources drops to a specified extent, introducing a wait into the operation in which sequential portions of a storage media are to be accessed for writing of information.

2. A method as in claim 1 wherein the measure of relative availability of storage system resources are stored in a table based on one of a group of storage media or a sequential task.

3. A method as in claim 2 wherein the table includes measures of allocated capacity and current capacity.

4. A method as in claim 2 wherein the table includes a measure of cache memory size available and throughput available.

5. A method as in claim 1 wherein the wait has a predetermined duration.

6. A method as in claim 1 wherein the duration of the wait is determined dynamically based upon the then available system resources.

7. In a storage system operating under computer control and coupled to a host to receive information to be stored, a method comprising:

in the storage system, monitoring communications between the host and the storage system to determine a measure of throughput requested by the host in having the storage system write data within the storage system; and

sending to the host a request to wait if the measure of throughput exceeds a specified quantity.

8. A method as in claim 7 wherein the data to be written in the storage system is first supplied to a cache memory within the storage system, and later written to storage media in the storage system.

9. A method as in claim 7 further comprising also storing the information in a secondary storage system.

10. A method as in claim 9 wherein the information is stored in a secondary storage system synchronously with being written to the storage media.

11. A method as in claim 9 wherein the information is stored in a secondary storage system asynchronously with being written to the storage media.

12. A method as in claim 7 wherein the storage system comprises an array of hard disk drives.

13. In a storage system having a cache memory for storing information before the information is written to storage media in the storage system, the storage system operating under computer control, and coupled to a host to receive information to be stored, a method comprising:

monitoring the communications between the host and the storage system to determine a measure of remaining capacity of the cache memory, and

if the extent of cache memory remaining is determined to be inadequate, delaying the sending of data from the host.

14. A method as in claim 13 wherein the step of delaying comprises introducing delays into the communications between the host and the storage system.

15. A method for controlling writing of data in a storage system having a plurality of storage media, the method comprising:

analyzing a requested write operation to determine if the requested write operation calls for a sequential task or a random task;

if the requested write operation is a sequential task, storing information about the sequential task in a task management table;

determining, using information in the task management table, if throttling is needed to carry out the requested write operation; and

if throttling is needed, applying a throttling technique to the sequential task.

16. A method as in claim 15 wherein the determination of whether the requested write operation calls for a sequential task includes determination of whether the requested write operation involves a single group of storage media.

17. A method as in claim 15 wherein the determination of whether the requested write operation calls for a sequential task includes determination of whether the requested write operation involves more than a single group of storage media.

18. A method as in claim 17 wherein throttling is controlled based upon both the determination of a sequential task and whether more than a single group of storage media are to have data written to them.

19. A method as in claim 15 wherein the throttling technique is selected based upon data in a table of statistical data.

20. A method as in claim 15 wherein the throttling technique comprises inserting wait states into the write operation to delay it.

21. A method as in claim 20 wherein the step of inserting wait states into the write operation comprises inserting a predefined wait time into the write operation.

22. A method as in claim 20 wherein the step of inserting wait states into the write operation comprises calculating a wait time at the time the wait time is to be inserted into the write operation.

23. A method as in claim 20 wherein following use of the throttling technique normal operation is resumed to write any remaining data into the storage system.

24. A method as in claim 15 wherein the throttling technique comprises:

monitoring a cache memory into which data is stored before being written to the storage media; and

when a predetermined amount of the cache memory has been filled, waiting for the cache memory to have more space before additional data are stored in the cache memory.

25. A method as in claim 24 wherein following use of the throttling technique normal operation is resumed to write any remaining data into the storage system.

26. A method as in claim 15 wherein the table uses a measure of throughput to determine whether throttling is to be applied.

27. A method as in claim 16 wherein the table uses an indication of an amount of cache memory available to determine whether throttling is to be applied.

28. A method as in claim 16 wherein the table uses both a measure of throughput and an indication of an amount of cache memory available to determine whether throttling is to be applied.