Device for prioritized erasure of flash memory

• US 7,975,119 B2
• Filed: 05/03/2007
• Issued: 07/05/2011
• 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): Rutz; Jared I
• Application Number:
  US11/797,378
• Publication Number:
  US 20080059692A1
• Time in Patent Office: 1,524 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

Abstract

A storage device having prioritized-erasure capabilities including: a memory for storing data, the memory having at least one flash unit, wherein each flash unit has a plurality of blocks; and a controller configured: to write the data into the plurality of blocks; to assign an erasure-priority to each block, wherein the erasure-priority correlates with an erasure-priority of the data; and to erase the data in each block according to the erasure-priority of each block upon receiving an emergency-erase command. Preferably, the controller is configured to perform the writing of the data into the plurality of blocks in an arbitrary order in a first flash unit, and the writing into subsequent flash units is performed in correlation with the order in the first flash unit. Preferably, the erasing includes aborting erasure, before completing the erasure, for at least some of the plurality of blocks.

Claims

1. A non-volatile storage device having prioritized-erasure capabilities, the device comprising:

a storage memory for storing data in the storage device, said storage memory having a plurality of flash units, wherein each flash unit has a plurality of blocks; and

a storage-device controller in communication with the storage memory and residing within the non-volatile storage device, the storage-device controller configured to write data across blocks of different flash units and to assign an erasure priority to the data based on a position of the corresponding block the data is stored, the storage-device controller having a table stored therein, the table tracking the erasure priority of the data stored in each of the blocks, the storage-device controller mapping the erasure priority of the data to the corresponding block the data is stored in, wherein in response to an erase command the storage device controller partially erases the data within each block in parallel based on the mapping, such that the storage-device controller partially erases blocks of the plurality of flash units with the same erasure priority.

2. The device of claim 1, wherein said controller is configured to write the data in parallel across the blocks.

3. The device of claim 1, wherein said controller partially erases the data by assigning a fraction of an erase time required for each block.

4. The device of claim 3, wherein the fraction of the erase time is about 50%.

5. The device of claim 1, wherein said controller is configured to perform said writing of said data in an arbitrary order in a first flash unit, and said writing into subsequent flash units is performed in correlation with said order in said first flash unit.

6. The device of claim 1, wherein said controller is further configured to map the erasure priority after writing the data to corresponding blocks.

7. The device of claim 1, wherein the storage memory is one of a NOR type memory or a NAND type memory.

8. A hard-disk drive having prioritized-erasure capabilities, the drive compromising:

a storage memory for storing data in the hard-disk drive, said storage memory having a plurality of sectors; and

a storage-device controller in communication with the storage memory and residing within the hard-disk drive, the storage-device controller configured to write data across the plurality of sectors and to assign an erasure priority to the data based on a position of the corresponding sector the data is stored, the storage-device controller having a table stored therein, the table tracking the erasure priority of the data stored in each of the sectors, the storage device controller mapping the erasure priority of the data to the corresponding sector the data is stored in, wherein in response to an erase command the storage device controller partially erases the data within each sector in parallel based on the mapping, such that the storage-device controller partially erases sectors with the same erasure priority.

9. The hard disk drive of claim 8, wherein the controller partially erases the data by assigning a fraction of an erase time required for each sector.