SYSTEM AND METHOD FOR MAINTAINING A DATA REDUNDANCY SCHEME IN A SOLID STATE MEMORY IN THE EVENT OF A POWER LOSS

• US 20120151253A1
• Filed: 12/14/2010
• Published: 06/14/2012
• Est. Priority Date: 12/14/2010
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: HORN, ROBERT L.
• Granted Patent: US 8,615,681 B2
• Time in Patent Office: Days
• US Class Current: 714/6.22
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2211/1009 Cache, i.e. caches used in RAID system with parity
• CPC Class Codes: G06F 2212/262 configured as RAID
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

Embodiments of the invention are directed to systems and methods for reducing an amount of backup power needed to provide power fail safe preservation of a data redundancy scheme such as RAID that is implemented in solid state storage devices where new write data is accumulated and written along with parity data. Because new write data cannot be guaranteed to arrive in integer multiples of stripe size, a full stripe'"'"'s worth of new write data may not exist when power is lost. Various embodiments use truncated RAID stripes (fewer storage elements per stripe) to save cached write data when a power failure occurs. This approach allows the system to maintain RAID parity data protection in a power fail cache flush case even though a full stripe of write data may not exist, thereby reducing the amount of backup power needed to maintain parity protection in the event of power loss.

Claims

1. A solid-state storage subsystem comprising:

a non-volatile memory array;

a write cache for temporarily storing data to be written to the 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;

move data stored in the write cache to the non-volatile memory array, the data being moved in a size increment matching a pre-defined size of the data stripes in the data redundancy configuration; and

in response to detecting a start of a shutdown of the storage subsystem, move data in the write cache to the non-volatile memory array to create a partial data stripe that is smaller than the pre-defined stripe size when a quantity of the cached data is insufficient to create a data stripe of the pre-defined size, thereby reducing an amount of power needed to enable the controller to move data in the write cache to the non-volatile memory array.

2. The solid-state storage subsystem of claim 1, wherein the shutdown is triggered by a power interruption.

3. The solid-state storage subsystem of claim 2 further comprising a backup power source for supplying backup power to the storage subsystem in the event of a power interruption and wherein the controller is configured to use the backup power to move data in the write cache to the non-volatile memory array to create a partial data stripe, thereby reducing an amount of power in the backup power source needed to enable the controller to move data in the event of a power interruption.

4. The solid-state storage subsystem of claim 1, wherein the shutdown is triggered by a command from a host system in data communication with the storage subsystem.

5. The solid-state storage subsystem of claim 1, wherein the controller is further configured to store parity data related to the data moved from the write cache in the event of a power interruption in a first available memory location in the non-volatile memory array after a memory location of the partial data stripe, the first available memory location being outside of a range of pre-designated memory locations for storing parity data of the data stripes of the pre-defined size in the non-volatile memory array.

6. The solid-state storage subsystem of claim 1, wherein the controller is further configured to combine the partial data stripe with additional data stored in the write cache after the power interruption to create a data stripe of the pre-defined size.

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

8. A method of maintaining data redundancy in a solid-state storage subsystem in the event of a power interruption, 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 data to be written to the non-volatile memory array in a write cache of the solid-state storage subsystem;

moving data stored in the write cache to the non-volatile memory array, the data being moved in a size increment matching a pre-defined size of the data stripes in the data redundancy configuration; and

when a shutdown of the storage subsystem begins while a quantity of data in the write cache is less than the pre-defined data stripe size, writing the cached data to the non-volatile memory array to form a partial data stripe of the data redundancy configuration.

9. The method of claim 8, wherein writing the cached data to the non-volatile memory array uses a backup power source when the shutdown is triggered by a power interruption.

10. The method of claim 8, further comprising:

storing parity data related to the data moved from the write cache in the event of a power interruption in a first available memory location in the non-volatile memory array after a memory location of the partial data stripe, the first available memory location being outside of a range of pre-designated memory locations for storing parity data of the data stripes of the pre-defined size in the non-volatile memory array.

11. The method of claim 8, further comprising:

combining the partial data stripe with additional data stored in the write cache after the power interruption to create a data stripe of the pre-defined size.

12. The method of claim 8, wherein the filler data comprises system configuration data for solid-state storage subsystem.

13. The method of claim 8, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.

14. A solid-state storage subsystem comprising:

a non-volatile memory array;

a backup power source for supplying backup power to the storage subsystem in the event of a power interruption;

a controller configured to;

receive data to be written to the non-volatile memory array;

write the received data to the non-volatile memory array as a plurality of data stripes as part of a data redundancy configuration, each data stripe being of a pre-defined stripe size;

create parity data for each stripe; and

in response to detecting a power interruption to the storage subsystem,

use the backup power to write the received data as a partial data stripe that is smaller than the pre-defined stripe size when a quantity of the received data not yet written is insufficient to create a data stripe of the pre-defined size, and

create parity data for the partial data stripe, thereby reducing an amount of power in the backup power source needed to enable the controller to provide parity protection for the received data in the event of a power interruption.

15. The solid-state storage subsystem of claim 14, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.

16. The solid-state storage subsystem of claim 14, wherein the parity data is written in a memory location immediately adjacent to a memory location in which the partial data stripe is stored in the non-volatile memory array.