Method for prioritized erasure of flash memory

• US 20080056012A1
• Filed: 05/03/2007
• Published: 03/06/2008
• Est. Priority Date: 09/04/2006
• Status: Active Grant

• Current Assignee: Western Digital Israel Limited (Western Digital Corporation)
• Original Assignee: SanDisk IL Ltd. (Western Digital Corporation)
• Inventors: Erez, Eran
• Granted Patent: US 8,117,414 B2
• Time in Patent Office: Days
• US Class Current: 365/185.29
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 3/0623 in relation to content
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

A method for prioritized erasure of a non-volatile storage device, the method including the steps of: providing at least one flash unit of the storage device, wherein each flash unit has a plurality of blocks; writing data into the plurality of blocks; assigning an erasure-priority to each block, wherein the erasure-priority correlates with an erasure-priority of the data; and erasing the data in each block according to the erasure-priority of each block upon receiving an emergency-erase command. Preferably, the step of writing data into the plurality of blocks is performed in an arbitrary order in a first flash unit, and the step of writing into subsequent flash units is performed in correlation with the order in the first flash unit. Preferably, the step of erasing includes aborting erasure, before completing the erasure, for at least some of the plurality of blocks.

Claims

1. A method for prioritized erasure of a non-volatile storage device, the method comprising the steps of:

(a) providing at least one flash unit of the storage device, wherein each flash unit has a plurality of blocks;

(b) writing data into said plurality of blocks;

(c) assigning an erasure-priority to each said block, wherein said erasure-priority correlates with an erasure-priority of said data; and

(d) erasing said data in said each block according to said erasure-priority of said each block upon receiving an emergency-erase command.

2. The method of claim 1, wherein said step of writing is performed on arbitrarily-selected blocks, and said step of assigning is performed according to said erasure-priority of said data.

3. The method of claim 1, wherein said step of assigning is performed prior to said step of writing, and said step of writing is performed according to said erasure-priority of said each block.

4. The method of claim 1, wherein said step of writing data into said plurality of blocks is performed in an arbitrary order in a first said flash unit, and said step of writing into subsequent said flash units is performed in correlation with said order in said first flash unit.

5. The method of claim 4, wherein said step of assigning includes assigning a common erasure-priority to blocks having a common relative position in each respective said flash unit.

6. The method of claim 1, the method further comprising the steps of:

(e) storing a log of said erasure-priority for said each block; and

(f) erasing said data in said each block according to said erasure-priority stored in said log upon receiving said emergency-erase command.

7. The method of claim 1, wherein said step of erasing includes aborting erasure, before completing said erasure, for at least some of said plurality of blocks.

8. A method for prioritized erasure of a hard-disk drive, the method comprising the steps of:

(a) providing at least two sectors of the hard-disk drive;

(b) writing data into said at least two sectors;

(c) assigning an erasure-priority to each said sector, wherein said erasure-priority correlates with an erasure-priority of said data; and

(d) erasing said data in said each sector according to said erasure-priority of said each sector upon receiving an emergency-erase command.