Cache Management Including Solid State Device Virtualization

• US 20130042056A1
• Filed: 08/10/2012
• Published: 02/14/2013
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Shats, Serge, Sanford, Steven Ted
• Granted Patent: US 9,323,659 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/0871 Allocation or management of cache space
• CPC Class Codes: G06F 2212/1016 Performance improvement
• CPC Class Codes: G06F 2212/1044 Space efficiency improvement
• CPC Class Codes: G06F 2212/222 Non-volatile memory
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 2212/7204 Capacity control, e.g. partitioning, end-of-life degradation
• CPC Class Codes: G06F 2212/7207 management of metadata or control data

Abstract

A method of caching data is performed by a respective computer having one or more processors storing one or more storage management programs for execution by the one or more processors, non-volatile secondary storage and non-volatile cache memory. The method includes receiving from the non-volatile cache memory information identifying an amount of available storage in the non-volatile cache memory, and identifying a size of the management units in the non-volatile cache memory. The method further includes identifying write requests to write data to the non-volatile cache memory, sequentially writing to the non-volatile cache memory the write data for the identified write requests, to sequentially arranged locations in an address space of the non-volatile cache memory, and storing in memory metadata that maps the addresses or storage offsets of the write data to respective locations in the address space of the non-volatile cache memory.

Claims

1. A method of caching data in a computer system having one or more processors, memory storing one or more storage management programs for execution by the one or more processors, non-volatile secondary storage and non-volatile cache memory, the non-volatile cache memory including a controller responsive to commands sent by the one or more processors of the computer system, the method comprising:

receiving from the non-volatile cache memory information identifying an amount of available storage in the non-volatile cache memory, and identifying a size of the management units in the non-volatile cache memory;

identifying write requests to write data to the non-volatile cache memory, each identified write request including an address or storage offset and write data;

sequentially writing to the non-volatile cache memory the write data for the identified write requests, wherein sequentially writing comprises writing to sequentially arranged locations in an address space of the non-volatile cache memory; and

storing in the computer system metadata that maps the addresses or storage offsets of the write data to respective locations in the address space of the non-volatile cache memory.

2. The method of claim 1, wherein identifying write requests to write data to the non-volatile cache memory comprises:

receiving write requests to write data to non-volatile storage, each write request including an address or storage offset and write data;

identifying a subset of the received write requests in accordance with caching criteria.

3. The method of claim 1, wherein sequentially writing comprises sending write commands to the controller of the non-volatile cache memory identifying the sequentially arranged locations within the non-volatile cache memory, without regard to addresses or storage offsets associated with the write data in another address space used by the computer system.

4. The method of claim 1, further comprising maintaining, at the computer system, a write pointer, a clean pointer and a flush pointer, said pointers corresponding to boundaries of unused, clean and dirty regions of the non-volatile cache memory, said pointers identifying distinct locations in the predefined sequence of available management units in the non-volatile cache memory, said maintaining including advancing the write pointer as write data is sequentially written to the non-volatile cache memory.

5. The method of claim 4, wherein

the received information identifying an amount of available storage in the non-volatile cache memory comprises receiving information identifying a size of the address space of the non-volatile cache memory and receiving information identifying an amount of said address space corresponding to unavailable management units in the non-volatile cache memory;

the size of said address space of the non-volatile cache memory remains fixed throughout performance of the method; and

said maintaining further comprises maintaining said pointers so as to maintain said unused region at a size that is greater than the amount of said address space corresponding to unavailable management units in the non-volatile cache memory.

6. The method of claim 1, wherein said maintaining includes sending commands to the non-volatile cache memory to flush data in the dirty region of the non-volatile cache memory to said non-volatile secondary storage, and to advance the flush pointer, thereby moving a shared boundary of the clean and dirty regions.

7. The method of claim 1, wherein said maintaining includes sending commands to the non-volatile cache memory to invalidate data in the clean region of the non-volatile cache memory, and to advance the clean pointer, thereby moving a shared boundary of the clean and unused regions.

8. The method of claim 7, wherein the commands to invalidate data in the clean region comprise commands to erase corresponding management units in the non-volatile cache memory.

9. The method of claim 1, wherein the received information identifying an amount of available storage in the non-volatile cache memory comprises receiving information identifying a size of the address space of the non-volatile cache memory.

10. The method of claim 9, wherein the address space of the non-volatile cache memory comprises a contiguous virtual address space that is mapped by the non-volatile cache memory to physical memory in the non-volatile cache memory.

11. The method of claim 9, wherein the address space of the non-volatile cache memory comprises a virtual address space, and the address or storage offset in said identified write requests comprises addresses or offsets in an address space of the non-volatile secondary storage.

12. The method of claim 1, wherein the non-volatile cache memory comprises solid state storage.

13. The method of claim 1, wherein the non-volatile cache memory comprises flash memory.

14. The method of claim 1, wherein the non-volatile secondary storage comprises one or more hard disk storage devices.

15. A computer system, comprising:

memory storing one or more programs, the one or more programs including one or more storage management programs;

one or more processors for executing instructions in the one or more programs stored in memory;

an interface to non-volatile secondary storage; and

non-volatile cache memory, the non-volatile cache memory including a controller responsive to commands sent by the one or more processors of the computer system;

the one or more storage management programs comprising instructions that, when executed by the one or more processors, cause the computer system to;

receive from the non-volatile cache memory information identifying an amount of available storage in the non-volatile cache memory, and identifying a size of the management units in the non-volatile cache memory;

identify write requests to write data to the non-volatile cache memory, each identified write request including an address or storage offset and write data;

sequentially write to the non-volatile cache memory the write data for the identified write requests, wherein sequentially writing comprises writing to sequentially arranged locations in an address space of the non-volatile cache memory; and

store in said memory metadata that maps the addresses or storage offsets of the write data to respective locations in the address space of the non-volatile cache memory.

16. The computer system of claim 15, wherein identifying write requests to write data to the non-volatile cache memory comprises:

receiving write requests to write data to non-volatile storage, each write request including an address or storage offset and write data;

identifying a subset of the received write requests in accordance with caching criteria.

17. The computer system of claim 15, wherein sequentially writing comprises sending write commands to the controller of the non-volatile cache memory identifying the sequentially arranged locations within the non-volatile cache memory, without regard to addresses or storage offsets associated with the write data in another address space used by the computer system.

18. A non-volatile computer readable storage medium storing one or more storage management programs comprising instructions that, when executed by one or more processors of a computer system that includes the one or more processors, non-volatile secondary storage and non-volatile cache memory, the non-volatile cache memory including a controller responsive to commands sent by the one or more processors of the computer system, cause the computer system to:

receive from the non-volatile cache memory information identifying an amount of available storage in the non-volatile cache memory, and identifying a size of the management units in the non-volatile cache memory;

identify write requests to write data to the non-volatile cache memory, each identified write request including an address or storage offset and write data;

sequentially write to the non-volatile cache memory the write data for the identified write requests, wherein sequentially writing comprises writing to sequentially arranged locations in an address space of the non-volatile cache memory; and

store in said memory metadata that maps the addresses or storage offsets of the write data to respective locations in the address space of the non-volatile cache memory.

19. The non-volatile computer readable storage medium of claim 18, wherein identifying write requests to write data to the non-volatile cache memory comprises:

receiving write requests to write data to non-volatile storage, each write request including an address or storage offset and write data;

identifying a subset of the received write requests in accordance with caching criteria.

20. The non-volatile computer readable storage medium of claim 18, wherein sequentially writing comprises sending write commands to the controller of the non-volatile cache memory identifying the sequentially arranged locations within the non-volatile cache memory, without regard to addresses or storage offsets associated with the write data in another address space used by the computer system.