Methods and systems for reducing churn in flash-based cache

• US 9,213,628 B2
• Filed: 07/14/2010
• Issued: 12/15/2015
• Est. Priority Date: 07/14/2010
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Nimble Storage (Hewlett-Packard Enterprise Company)
• Inventors: Maheshwari, Umesh, Mehta, Varun
• Primary Examiner(s): MACKALL, LARRY T
• Application Number:
  US12/836,520
• Publication Number:
  US 20120017034A1
• Time in Patent Office: 1,980 Days
• Field of Search: 711/113, 711/138, 711/103
• US Class Current: 1/1
• 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 flash memory-based cache and a disk-based storage unit, 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 disk-based storage unit at a substantially similar data rate as from the flash memory-based cache, writing the sequentially-accessed data only to the disk-based storage unit so as to reduce the amount of data written to the flash memory-based cache; and

if the sequentially-accessed data cannot be read from the disk-based storage unit at a substantially similar data rate as from the flash memory-based cache, writing the sequentially-accessed data to both the flash memory-based cache and the disk-based storage unit.

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 flash memory-based cache, a disk-based storage unit and a controller, the controller (i) communicatively coupled to the flash memory-based cache and the disk-based storage unit;

and (ii) configured to;

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

perform a selective caching of the sequentially-accessed data, wherein the selective caching comprises;

if the sequentially-accessed data can be read from the disk-based storage unit at a substantially similar data rate as from the flash memory-based cache, writing the sequentially-accessed data only to the disk-based storage unit so as to reduce the amount of data written to the flash memory-based cache; and

if the sequentially-accessed data cannot be read from the disk-based storage unit at a substantially similar data rate as from the flash memory-based cache, writing the sequentially-accessed data to both the flash memory-based cache and the disk-based storage unit.

6. The storage device of claim 5, wherein a size of the sequentially-accessed data is greater than 1 megabyte (MB).

7. A non-transitory computer-readable storage medium comprising software instructions that, when executed by a controller of a storage device, cause the controller to:

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

perform a selective caching of the sequentially-accessed data, wherein the selective caching comprises;

if the sequentially-accessed data can be read from a disk-based storage unit of the storage device at a substantially similar data rate as from a flash memory-based cache of the storage device, writing the sequentially-accessed data only to the disk-based storage unit so as to reduce the amount of data written to the flash memory-based cache; and

if the sequentially-accessed data cannot be read from the disk-based storage unit at a substantially similar data rate as from the flash memory-based cache, writing the sequentially-accessed data to both the flash memory-based cache and the disk-based storage unit.

8. The non-transitory computer-readable storage medium of claim 7, wherein a size of the sequentially-accessed data is greater than 1 megabyte (MB).