Data Storage System with Stale Data Mechanism and Method of Operation Thereof

• US 20150046665A1
• Filed: 07/15/2014
• Published: 02/12/2015
• Est. Priority Date: 08/07/2013
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Smart Storage Systems Incorporated (Western Digital Corporation)
• Inventors: Higgins, James M., Virgin, Theron W.
• Granted Patent: US 9,448,946 B2
• Time in Patent Office: Days
• US Class Current: 711/158
• CPC Class Codes: G06F 12/023 Free address space management
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

Systems, methods and/or devices are used to enable a stale data mechanism. In one aspect, the method includes (1) receiving a write command specifying a logical address to which to write, (2) determining whether a stale flag corresponding to the logical address is set, (3) in accordance with a determination that the stale flag is not set, setting the stale flag and releasing the write command to be processed, and (4) in accordance with a determination that the stale flag is set, detecting an overlap, wherein the overlap indicates two or more outstanding write commands are operating on the same memory space.

Claims

1. A method of operation of a data storage system comprising:

receiving a write command specifying a logical address to which to write;

determining whether a stale flag corresponding to the logical address is set;

in accordance with a determination that the stale flag is not set, setting the stale flag and releasing the write command to be processed; and

in accordance with a determination that the stale flag is set, detecting an overlap, wherein the overlap indicates two or more outstanding write commands are operating on the same memory space.

2. The method of claim 1, further comprising:

in response to detecting an overlap, performing a write-merge operation, wherein the write-merge operation consolidates the two or more outstanding write commands to the logical address.

3. The method of claim 1, further comprising:

completing processing of the write command; and

updating the stale flag.

4. The method of claim 3, wherein updating the stale flag includes clearing the stale flag.

5. The method of claim 3, wherein the stale flag is a count of a number of outstanding write commands associated with a respective logical address, and updating the stale flag includes decrementing the count.

6. The method of claim 1, further comprising:

receiving a read command specifying a second logical address from which to read;

determining whether a second stale flag corresponding to the second logical address is set;

in accordance with a determination that the second stale flag is not set, performing the read command, wherein performing the read command includes reading data from a physical address corresponding to the second logical address, wherein the physical address is determined using a logical-to-physical table; and

in accordance with a determination that the second stale flag is set, skipping performance of the read command until the second stale flag is not set.

7. The method of claim 6, further comprising:

in accordance with a determination that the second stale flag is set, prioritizing a stale write, wherein completion of the stale write clears the second stale flag.

8. The method of claim 1, further comprising:

receiving a read command specifying a second logical address from which to read;

determining whether a second stale flag corresponding to the second logical address is set;

in accordance with a determination that the second stale flag is not set, performing the read command, wherein performing the read command includes reading data from a physical address corresponding to the second logical address, wherein the physical address is determined using a logical-to-physical table; and

in accordance with a determination that the second stale flag is set, servicing the read command by reading data from in-flight write data for the second logical address.

9. The method of claim 1, wherein each logical address of a plurality of logical addresses has a corresponding stale flag and each stale flag is stored in a logical-to-physical table used for mapping logical addresses to physical addresses.

10. The method of claim 1, wherein each logical address of a plurality of logical addresses has a corresponding stale flag and each stale flag is stored in a separate table from a logical-to-physical table used for mapping logical addresses to physical addresses.

11. A data storage system comprising:

one or more processors; and

memory storing one or more programs to be executed by the one or more processors, the one or more programs comprising instructions for;

receiving a write command specifying a logical address to which to write;

determining whether a stale flag corresponding to the logical address is set;

in accordance with a determination that the stale flag is not set, setting the stale flag and releasing the write command to be processed; and

in accordance with a determination that the stale flag is set, detecting an overlap, wherein the overlap indicates two or more outstanding write commands are operating on the same memory space.

12. The data storage system of claim 11, wherein the one or more programs further comprise instructions for:

in response to detecting an overlap, performing a write-merge operation, wherein the write-merge operation consolidates the two or more outstanding write commands to the logical address.

13. The data storage system of claim 11, wherein the one or more programs further comprise instructions for:

completing processing of the write command; and

updating the stale flag.

14. The data storage system of claim 11, wherein the one or more programs further comprise instructions for:

receiving a read command specifying a second logical address from which to read;

determining whether a second stale flag corresponding to the second logical address is set;

in accordance with a determination that the second stale flag is not set, performing the read command, wherein performing the read command includes reading data from a physical address corresponding to the second logical address, wherein the physical address is determined using a logical-to-physical table; and

in accordance with a determination that the second stale flag is set, skipping performance of the read command until the second stale flag is not set.

15. The data storage system of claim 14, wherein the one or more programs further comprise instructions for:

in accordance with a determination that the second stale flag is set, prioritizing a stale write, wherein completion of the stale write clears the second stale flag.

16. The data storage system of claim 11, wherein the one or more programs further comprise instructions for:

receiving a read command specifying a second logical address from which to read;

determining whether a second stale flag corresponding to the second logical address is set;

in accordance with a determination that the second stale flag is not set, performing the read command, wherein performing the read command includes reading data from a physical address corresponding to the second logical address, wherein the physical address is determined using a logical-to-physical table; and

in accordance with a determination that the second stale flag is set, servicing the read command by reading data from in-flight write data for the second logical address.

17. A non-transitory computer readable storage medium, storing one or more programs configured for execution by one or more processors of a data storage system, the one or more programs including instructions for:

receiving a write command specifying a logical address to which to write;

determining whether a stale flag corresponding to the logical address is set;

in accordance with a determination that the stale flag is not set, setting the stale flag and releasing the write command to be processed; and

in accordance with a determination that the stale flag is set, detecting an overlap, wherein the overlap indicates two or more outstanding write commands are operating on the same memory space.

18. The non-transitory computer readable storage medium of claim 17, wherein the one or more programs further include instructions for:

in response to detecting an overlap, performing a write-merge operation, wherein the write-merge operation consolidates the two or more outstanding write commands to the logical address.

19. The non-transitory computer readable storage medium of claim 17, wherein the one or more programs further include instructions for:

completing processing of the write command; and

updating the stale flag.

20. The non-transitory computer readable storage medium of claim 17, wherein the one or more programs further include instructions for:

receiving a read command specifying a second logical address from which to read;

determining whether a second stale flag corresponding to the second logical address is set;

in accordance with a determination that the second stale flag is not set, performing the read command, wherein performing the read command includes reading data from a physical address corresponding to the second logical address, wherein the physical address is determined using a logical-to-physical table; and

in accordance with a determination that the second stale flag is set, skipping performance of the read command until the second stale flag is not set.