Mass storage device and method for offline background scrubbing of solid-state memory devices

• US 8,370,720 B2
• Filed: 08/19/2010
• Issued: 02/05/2013
• Est. Priority Date: 08/19/2009
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: OCZ Technology Group, Inc. (Toshiba Corporation)
• Inventors: Allen, William J.
• Primary Examiner(s): Riad, Amine
• Application Number:
  US12/859,595
• Publication Number:
  US 20110231730A1
• Time in Patent Office: 901 Days
• Field of Search: 714/773
• US Class Current: 714/773
• CPC Class Codes: G06F 11/106 Correcting systematically all correctable errors, i.e. scrubbing
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control

Abstract

A solid-state mass storage device and method for its operation that includes performing preemptive scrubbing of data during offline periods or disconnects from a host system to which the mass storage device is attached. The device includes a system interface adapted to connect the drive to a host system, at least one nonvolatile memory device, controller means through which data pass when being written to and read from the memory device, a volatile memory cache, a system logic device, and an integrated power source for powering the drive. The system logic device is configured to operate when the drive is not functionally connected to a host system, execute copy commands without accessing a host system, and prioritize preemptive scrubbing of addresses in the memory device on the basis of risk of data loss based on one or more parameters logged by the internal system logic device.

Claims

1. A self-powered solid-state drive configured to perform offline scrubbing of solid-state mass storage media, the drive comprising:

a package comprising a printed circuit board;

a system interface coupled to the circuit board and adapted to connect the drive to a host system;

at least one nonvolatile memory device on the circuit board;

controller means on the circuit board through which data pass when being written to and read from the memory device;

a volatile memory cache on the circuit board;

means on the circuit board for performing the function of a real-time clock on the circuit board;

a system logic device configured to operate when the drive is not functionally connected to a host system, execute copy commands without accessing a host system, and prioritize preemptive scrubbing of addresses in the memory device on the basis of risk of data loss based on one or more parameters logged by the internal system logic device; and

an integrated power source on the circuit board for powering the drive.

2. The self-powered solid-state drive of claim 1, wherein the power source is a battery or a supercapacitor.

3. The self-powered solid-state drive of claim 1, wherein the system logic device comprises a processor that executes the copy commands without accessing a host system and prioritizes the preemptive scrubbing of the addresses in the memory device, and integrated memory for recording the one or more parameters.

4. The self-powered solid-state drive of claim 1, wherein the system logic device comprises the means for performing the function of a real-time clock.

5. The self-powered solid-state drive of claim 1, wherein the system logic device is a system-on-a-card or a system-on-a-chip.

6. The self-powered solid-state drive of claim 5, wherein the controller means is a discrete component on the circuit board separate from the system logic device.

7. The self-powered solid-state drive of claim 5, wherein the controller means is integrated on the system logic device.

8. The self-powered solid-state drive of claim 1, wherein the system logic device is adapted to initiate the preemptive scrubbing of the addresses in the memory device at a predetermined time after the drive is no longer functionally connected to a host system.

9. The self-powered solid-state drive of claim 1, wherein the one or more parameters used by the system logic device to prioritize the preemptive scrubbing of the addresses in the memory device comprise at least one of the following parameters:

age of data at an address, number and frequency of accesses of data at an address, time to program a block of memory of the solid-state mass storage media, time to erase a block of memory of the solid-state mass storage media, and number of errors corrected through ECC algorithms.

10. The self-powered solid-state drive of claim 1, wherein the one or more parameters used by the system logic device to prioritize the preemptive scrubbing of the addresses in the memory device comprise the physical distribution of read and write accesses to a plurality of addresses in the memory device in proximity to another address in the memory device.

11. A method of performing an offline scrubbing operation using the self-powered solid-state drive of claim 1, the method comprising prioritizing the scrubbing operation based on at least one of the parameters analyzed by the system logic device and chosen from the group consisting of:

age of data at an address of the solid-state mass storage media;

number and frequency of accesses of data at an address of the solid-state mass storage media;

time to program a block of memory of the solid-state mass storage media;

time to erase a block of memory of the solid-state mass storage media; and

number of errors corrected through ECC algorithms to identify data corruption at an address of the solid-state mass storage media, proactively restore data based on ECC algorithms, and copy the restored data to a new address of the solid-state mass storage media.

12. A method of performing offline scrubbing solid-state mass storage media of a self-powered solid-state drive, the method comprising:

initiating a scrubbing operation to be performed by a system logic device on blocks of memory of the solid-state mass storage media following a predetermined period of time after the drive has gone offline from a host system; and

prioritizing the scrubbing operation based on at least one parameter analyzed by the system logic device and chosen from the group consisting of;

age of data at an address of the solid-state mass storage media;

number and frequency of accesses of data at an address of the solid-state mass storage media;

time to program a block of memory;

time to erase a block of memory; and

number of errors corrected through ECC algorithms;

performing the scrubbing operation with the system logic device, the scrubbing operation comprising determining whether data in a first block of memory at a first address are at risk of data loss, moving the data in the first block to a second block at a second address, and then invalidating the first block.

13. The method of claim 12, further comprising identifying data corruption at an address of the solid-state mass storage media, proactively restoring data based on ECC algorithms, and copying the restored data to a new address of the solid-state mass storage media.

14. The method of claim 12, wherein the system logic device comprises a processor that executes copy commands without accessing a host system and prioritizes the scrubbing operation, and integrated memory for recording the at least one parameter.

15. The method of claim 12, wherein the system logic device calculates the predetermined period of time.

16. The method of claim 12, wherein the time to program and the time to erase are used to determine the viability of a block in an active memory pool of the solid-state mass storage media and move the block from the active memory pool to a reserve memory pool of the solid-state mass storage media if the time to program or time to erase exceeds a threshold.

17. The method of claim 16, wherein the block in the reserve pool is checked to determine recoverability of the block caused by environmental factors.