Flash drive fast wear leveling

• US 7,853,749 B2
• Filed: 08/30/2006
• Issued: 12/14/2010
• Est. Priority Date: 09/01/2005
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Kolokowsky, Steve
• Primary Examiner(s): Ellis, Kevin L
• Assistant Examiner(s): BRADLEY, MATTHEW A
• Application Number:
  US11/468,569
• Publication Number:
  US 20070050536A1
• Time in Patent Office: 1,567 Days
• Field of Search: 711/103
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically

Abstract

A system and method comprising a non-volatile memory including one or more memory blocks to store data, a controller to allocate one or more of the memory blocks to store data, and a wear-leveling table populated with pointers to unallocated memory blocks in the non-volatile memory, the controller to identify one or more pointers in the wear-leveling table and to allocate the unallocated memory blocks associated with the identified pointers for the storage of data.

Claims

1. A method comprising:

populating a wear-leveling table with pointers to one or more memory blocks in a flash memory, where the pointers are associated with erased memory blocks or memory blocks that are faulty;

identifying at least one pointer in the wear-leveling table associated with an erased memory block;

storing data to the memory block associated with the identified pointer;

identifying erased memory blocks and faulty memory blocks in the flash memory;

comparing a number of identified erased memory blocks and faulty memory blocks to a threshold; and

populating the wear-leveling table responsive to the comparing or initializing the flash memory with pointers to the memory blocks responsive to the comparing.

2. The method of claim 1 includes erasing data stored in one or more of the memory blocks responsive to the identifying at least one pointer in the wear-leveling table and prior to storing data to the memory block associated with the identified pointer.

3. The method of claim 1 includes prioritizing the pointers in the wear-leveling table according to when the memory blocks associated with the pointers were erased.

4. The method of claim 3 includes accessing the wear-leveling table for pointers according to the prioritizing.

5. The method of claim 1 includes prioritizing the pointers in the wear-leveling table according to the number of write operations performed on the memory blocks associated with the pointers.

6. The method of claim 1 includes initializing a logical-to-physical table with pointers to the memory blocks in the flash memory concurrently to populating the wear-leveling table with pointers associated with the erased memory blocks.

7. The method of claim 6 includes allocating the memory blocks associated with the pointers in the logical-to-physical table prior to accessing the wear-leveling table for pointers to erased memory blocks.

8. A method comprising:

populating a wear-leveling table with pointers to one or more memory blocks in a flash memory, where the pointers are associated with erased memory blocks or memory blocks that are faulty;

receiving a write command identifying a zone of the flash memory to store data;

determining the wear-leveling table does not correspond to the identified zone;

re-populating the wear-leveling table with pointers to memory blocks corresponding to the identified zone;

identifying at least one pointer in the re-populated wear-leveling table associated with an erased memory block; and

storing data to the memory block associated with the identified pointer.

9. The method of claim 8, comprising:

identifying erased memory blocks and faulty memory blocks in the flash memory;

comparing a number of identified erased memory blocks and faulty memory blocks to a threshold; and

populating the wear-leveling table responsive to the comparing.

10. The method of claim 8, comprising:

identifying erased memory blocks and faulty memory blocks in the flash memory;

comparing a number of identified erased memory blocks and faulty memory blocks to a threshold; and

initializing the flash memory with pointers to the memory blocks responsive to the comparing.