System and method for data error recovery in a solid state subsystem

• US 8,700,950 B1
• Filed: 02/11/2011
• Issued: 04/15/2014
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Syu, Mei-Man L.
• Primary Examiner(s): Manoskey, Joseph D
• Application Number:
  US13/025,980
• Time in Patent Office: 1,159 Days
• Field of Search: 714/6.1, 714/6.2, 714/6.21, 714/6.22, 714/6.24, 714/42, 714/48, 714/54
• US Class Current: 714/6.24
• CPC Class Codes: G06F 11/0727 in a storage system, e.g. in a DASD or network based storage system drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/1008 in individual solid state devices G06F11/1004 takes precedence
• CPC Class Codes: G06F 11/1016 Error in accessing a memory location, i.e. addressing error
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 2211/109 Sector level checksum or ECC, i.e. sector or stripe level checksum or ECC in addition to the RAID parity calculation

Abstract

Systems and methods are disclosed for recovering from a data access error encountered in data stripes implemented in a data redundancy scheme (e.g., RAID) in a solid state storage device. In one embodiment, the storage device holds parity data in a temporary, volatile memory such as a RAM and writes the parity data to the non-volatile memory when a full stripe'"'"'s worth of new write data has been written to the non-volatile memory. In one embodiment, upon detecting that a data access error has occurred in a partially written stripe, the storage device initiates a write of the parity data for the partially written stripe to the non-volatile memory and executes a RAID recovery procedure using the newly written parity data to attempt to recover from the detected error. This approach allows for a recovery from the data access error without waiting for the full stripe to be written.

Claims

1. A solid-state storage subsystem comprising:

a non-volatile memory array;

a controller configured to implement a data redundancy configuration with a plurality of data stripes in the non-volatile memory array; and

a volatile memory for temporarily storing data to be written to the non-volatile memory array and parity data for one or more of the data stripes in the non-volatile memory array, wherein each of the plurality of data stripes is of a pre-defined stripe size and wherein the controller is configured to write parity data for a data stripe to the non-volatile memory array when data already written to the non-volatile memory for the data stripe reaches the pre-defined stripe size;

wherein the controller is further configured to;

detect an occurrence of a data access error in one of the plurality of data stripes for which parity data has not been written to the non-volatile memory array; and

in response to detecting an occurrence of a data access error, move the parity data for the data stripe causing the error from the volatile memory to the non-volatile memory array ahead of a scheduled writing of the parity data, and

attempt to correct the data access error with the newly written parity data.

2. The solid-state storage subsystem of claim 1, wherein the writing of the parity data creates a partial data stripe that is smaller than the pre-defined stripe size.

3. The solid-state storage subsystem of claim 2, wherein the controller is further configured to combine the partial data stripe with additional data to create an expanded stripe of the pre-defined stripe size and write new parity data for the expanded stripe.

4. The solid-state storage subsystem of claim 1, wherein the data access error is an ECC read error.

5. The solid-state storage subsystem of claim 1, wherein the data access error is a program error.

6. The solid-state storage subsystem of claim 1, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.

7. A method of recovering from a data access error in a solid-state storage subsystem, the method comprising:

implementing a data redundancy configuration with a plurality of data stripes in a non-volatile memory array of the solid-state storage subsystem;

temporarily storing, in a volatile memory of the solid-state storage subsystem, data to be written to the non-volatile memory array and parity data associated with said data to be written;

detecting an occurrence of a data access error in one of the plurality of data stripes for which parity data has not been written to the non-volatile memory array; and

in response to detecting the occurrence of a data access error, moving the parity data for said data stripe in which the data access error occurred from the volatile memory to the non-volatile memory array to make said parity data available for attempting to correct the data access error in advance of a scheduled write for the parity data, the scheduled write corresponding to a time when the data already written to the non-volatile memory for said data stripe reaches a pre-defined stripe size.

8. The method of claim 7, wherein each of the plurality of data stripes is of the pre-defined stripe size and wherein the writing of the parity data creates a partial data stripe that is smaller than the pre-defined stripe size.

9. The method of claim 7, further comprising:

combining the partial data stripe with additional data to create an expanded stripe of the pre-defined stripe size; and

writing new parity data for the expanded stripe.

10. The method of claim 7, wherein the data access error is an ECC read error.

11. The method of claim 7, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.

12. A solid-state storage subsystem comprising:

a non-volatile memory array;

a controller configured to implement a data redundancy configuration with a plurality of data stripes in the non-volatile memory array; and

volatile memory for temporarily storing data to be written to the non-volatile memory array and parity data for one or more of the data stripes in the non-volatile memory array;

wherein the controller is further configured to;

detect an occurrence of a data access error in one of the plurality of data stripes for which parity data has not been written to the non-volatile memory array; and

in response to detecting an occurrence of a data access error, move the parity data for the data stripe in which the data access error occurred from the volatile memory to the non-volatile memory array, in advance of a time when the data written to the non-volatile memory for the data stripe reaches a pre-defined stripe size, whereby the data access error can be corrected with the parity data.

13. The solid-state storage subsystem of claim 12, wherein the data access error is an ECC read error.

14. The solid-state storage subsystem of claim 12, wherein the data access error is a program error.

15. The solid-state storage subsystem of claim 12, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.