Method for prioritized erasure of flash memory

• US 8,117,414 B2
• Filed: 05/03/2007
• Issued: 02/14/2012
• 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
• Primary Examiner(s): Bradley, Matthew
• Application Number:
  US11/797,377
• Publication Number:
  US 20080056012A1
• Time in Patent Office: 1,748 Days
• Field of Search: 711/103, 711/158, 711/166, 713/194, 726/26
• US Class Current: 711/166
• 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:

providing a plurality of flash units within the storage device, wherein each of the flash units has a plurality of blocks controlled by a single controller contained within the storage device, each block having an erasure priority;

writing data in parallel across blocks of different flash units through the single controller, wherein an erasure priority is assigned to the data based on a position of the corresponding block the data is written;

logging the erasure priority of the data in each of the blocks in a table of the storage device after writing the data;

receiving an erase command from the single controller;

generating a logical erase slice identifying one of the blocks to be erased within each of the flash units, the identifying based on each one of the blocks of the logical erase slice having the same erasure priority, wherein at least one of the blocks to be erased has a different relative address within a flash unit than another one of the blocks; and

partially erasing the data within each block of the logical erase slice in parallel, wherein the partially erasing is executed according to the erasure priority and wherein the partially erasing is set for a time period that is a maximum of 50% of a full erase time period for a single block of the logical erase cycle, and wherein the data within each block remains partially erased.

2. The method of claim 1, wherein the writing is performed on arbitrarily-selected blocks.

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

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

5. The method of claim 1, further comprising:

continuing the erasing until all data having the same erasure priority is deleted; and

erasing additional logical erase slices in parallel for a next erasure priority.

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

providing a plurality of sectors of the hard-disk drive, each sector having an erasure priority, the hard disk drive. controlled by a single controller contained within the storage device;

writing data into the plurality of sectors through the single controller, wherein an erasure priority is assigned to the data based on a position of the corresponding block the data is written into;

logging the erasure priority of the data in each of the sectors in a table of the hard disk drive after writing the data;

receiving an erase command;

generating a logical erase slice identifying a plurality of the sectors to be erased within the hard disk drive, the identifying based on each of the plurality of the sectors of the logical erase slice having the same erasure priority; and

partially erasing the data within each sector of the logical erase slice in parallel, wherein the partially erasing is executed according to the erasure priority and wherein the partially erasing is set for a time period that is a maximum of 50% of a full erase time period for a single sector of the logical erase cycle, and wherein the data within each sector remains partially erased.