Methods and systems for reducing churn in a caching device

• US 10,216,638 B2
• Filed: 05/19/2017
• Issued: 02/26/2019
• Est. Priority Date: 07/14/2010
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Maheshwari, Umesh, Mehta, Varun
• Primary Examiner(s): Mackall, Larry T
• Application Number:
  US15/600,429
• Publication Number:
  US 20170270048A1
• Time in Patent Office: 648 Days
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/0888 using selective caching, e.g. bypass
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/1044 Space efficiency improvement
• CPC Class Codes: G06F 2212/222 Non-volatile memory
• CPC Class Codes: G06F 2212/28 Using a specific disk cache architecture
• CPC Class Codes: G06F 2212/466 Metadata, control data
• CPC Class Codes: G06F 2212/60 Details of cache memory
• CPC Class Codes: G06F 2212/604 Details relating to cache allocation
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays

Abstract

A storage device includes a flash memory-based cache for a hard disk-based storage device and a controller that is configured to limit the rate of cache updates through a variety of mechanisms, including determinations that the data is not likely to be read back from the storage device within a time period that justifies its storage in the cache, compressing data prior to its storage in the cache, precluding storage of sequentially-accessed data in the cache, and/or throttling storage of data to the cache within predetermined write periods and/or according to user instruction.

Claims

1. A method for a storage device having a caching device and a backend storage device, the method comprising:

receiving data at the storage device, the data including sequentially-accessed data; and

performing, by a controller of the storage device, a selective caching of the sequentially-accessed data, wherein the selective caching comprises;

if the sequentially-accessed data can be read from the backend storage device at a substantially similar data rate as from the caching device, writing the sequentially-accessed data only to the backend storage device so as to reduce the amount of data written to the caching device; and

if the sequentially-accessed data cannot be read from the backend storage device at a substantially similar data rate as from the caching device, writing the sequentially-accessed data to both the caching device and the backend storage device.

2. The method of claim 1, wherein a size of the sequentially-accessed data is greater than 1 megabyte (MB).

3. The method of claim 1, wherein the selective caching of the sequentially-accessed data comprises a selective write-through caching of the sequentially-accessed data.

4. The method of claim 1, wherein the selective caching of the sequentially-accessed data is applied on writes but is not applied on read misses.

5. A storage device, comprising:

a controller; and

a memory that stores instructions that, when executed by the controller, cause the controller to;

receive data to be stored in the storage device;

write an initial portion of the data to a caching device and a backend storage device;

while the initial portion is being written to the caching device and the backend storage device, monitor an amount of the initial portion that has been written sequentially;

determine whether the amount that has been written sequentially exceeds a predetermined threshold beyond which the data can be read from the caching device at a substantially similar data rate as from the backend storage device; and

if so, predict that the data is to be sequentially accessed, cease writing of the data to the caching device and write the remaining portion of the data only to the backend storage device so as to reduce the amount of data written to the caching device.

6. The storage device of claim 5, wherein the received data comprises compressed data.

7. The storage device of claim 5, wherein the memory stores instructions that, when executed by the controller, cause the controller to compress the received data prior to writing the compressed data to the caching device.

8. The storage device of claim 7, wherein the compression of the received data by the controller produces variable sized blocks of data.

9. The storage device of claim 5, wherein the memory stores instructions that, when executed by the controller, cause the controller to throttle updates to the caching device by permitting only a threshold number of writes per write period to the caching device, wherein each write period comprises a period of fixed interval.

10. The storage device of claim 5, wherein the memory stores instructions that, when executed by the controller, cause the controller to throttle updates to the caching device in accordance with user instructions concerning whether or not the data is to be cached.

11. The storage device of claim 5, wherein the memory stores instructions that, when executed by the controller, cause the controller to throttle updates to the caching device in accordance with user instructions concerning a data type of the data.

12. A non-transitory computer-readable storage medium including a set of instructions stored thereon, which when executed by a storage device cause the storage device to:

receive data to be stored in the storage device, the storage device having a caching device and a backend storage device;

write an initial portion of the data to the caching device and the backend storage device;

while the initial portion is being written to the caching device and the backend storage device, monitor an amount of the initial portion that has been written sequentially;

determine whether the amount that has been written sequentially exceeds a predetermined threshold beyond which the data can be read from the caching device at a substantially similar data rate as from the backend storage device; and

if so, predict that the data is to be sequentially accessed, cease writing of the data to the caching device and write the remaining portion of the data only to the backend storage device so as to reduce the amount of data written to the caching device.

13. The non-transitory computer-readable storage medium of claim 12, further including instructions, which when executed by the storage device cause the storage device to compress the received data prior to writing the compressed data to the caching device.

14. The non-transitory computer-readable storage medium of claim 13, wherein the compression of the received data by the controller produces variable sized blocks of data.

15. The non-transitory computer-readable storage medium of claim 12, further including instructions, which when executed by the storage device cause the storage device to throttle updates to the caching device by permitting only a threshold number of writes per write period to the caching device, wherein each write period comprises a period of fixed interval.

16. The non-transitory computer-readable storage medium of claim 12, further including instructions, which when executed by the storage device cause the storage device to throttle updates to the caching device in accordance with user instructions concerning whether or not the data is to be cached.

17. The non-transitory computer-readable storage medium of claim 12, further including instructions, which when executed by the storage device cause the storage device to throttle updates to the caching device in accordance with user instructions concerning a data type of the data.

18. The non-transitory computer-readable storage medium of claim 12, wherein the received data comprises compressed data.