System and method for wear leveling in a data storage device

• US 8,312,204 B2
• Filed: 01/23/2009
• Issued: 11/13/2012
• Est. Priority Date: 01/23/2009
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Zhang, Fumin, Malakapalli, Chris
• Primary Examiner(s): BATAILLE, PIERRE MICHE
• Application Number:
  US12/358,319
• Publication Number:
  US 20100191897A1
• Time in Patent Office: 1,390 Days
• Field of Search: 711/103, 711/218, 711/E12.001, 711/217, 711/E12.008
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 2212/7203 Temporary buffering, e.g. using volatile buffer or dedicated buffer blocks
• CPC Class Codes: G06F 2212/7211 Wear leveling

Abstract

The present disclosure provides a system and method for wear leveling. In one example, the method includes receiving first data to be stored to a first data storage medium and storing the first data to a first storage location in a nonvolatile data store of a second data storage medium comprising a solid-state memory. The method also includes setting a pointer to enable writing second data that is received to a next storage location in the nonvolatile data store. The next storage location comprises an address of the nonvolatile data store that is sequentially after an address of the first storage location. When the address of the first storage location is a last addressed location of the nonvolatile data store the pointer is set to enable writing the second data to a first addressed location of the nonvolatile data store. The method also includes writing the first data stored in the nonvolatile data store to the first data storage medium when a trigger occurs and preserving the pointer during the writing from the nonvolatile data store to the first data storage device such that the pointer enables writing the second data to the next storage location.

Claims

1. A method comprising:

receiving first data to be stored to a first data storage medium;

storing the first data to a first storage location in a nonvolatile data store of a second data storage medium comprising a solid-state memory;

setting a write pointer to direct writing second data that is received to a next sequential storage location in the nonvolatile data store, the next sequential storage location comprising an address of the nonvolatile data store that is sequentially after an address of the first storage location, wherein when the address of the first storage location is a last address location of the nonvolatile data store, the write pointer is set to enable writing the second data to a first addressed location of the nonvolatile data store;

writing the first data stored in the nonvolatile data store to the first data storage medium when a trigger occurs; and

preserving the write pointer during the writing from the nonvolatile data store to the first data storage medium such that the write pointer enables writing the second data to the next sequential storage location.

2. The method of claim 1, wherein the trigger comprises an indication of a quantity of data stored in the nonvolatile data store.

3. The method of claim 1, wherein the trigger comprises an indication that the write pointer is set to a specific address.

4. The method of claim 1, wherein the trigger comprises an indication of a length of time from a previous writing of the nonvolatile data store to the first data storage medium.

5. The method of claim 1, wherein writing the first data stored in the nonvolatile data store comprises flushing the data stored in the nonvolatile data store to the first data storage medium.

6. The method of claim 5, wherein flushing the data comprises:

retrieving the data from the nonvolatile data store;

sorting the data based on logical block addresses associated with the data; and

storing the sorted data to the first data storage medium based on the logical block addresses.

7. The method of claim 5, wherein flushing the data comprises accessing a translation component to map physical block addresses of the data to corresponding logical block addresses and erasing the data from the nonvolatile data store after the sorted data has been stored to the first data storage medium.

8. The method of claim 7, wherein the translation component comprises a tree structure having a plurality of nodes, each of the plurality of nodes representing information including a logical address, a physical address, and a number of sectors associated with data stored in the nonvolatile data store.

9. The method of claim 1, further comprising storing the write pointer in the nonvolatile data store.

10. The method of claim 1, wherein writing the first data comprises writing the first data to a user data region of the nonvolatile data store and writing a logical block address identifier associated with the first data to a spare region of the nonvolatile data store.

11. The method of claim 1, and further comprising:

receiving a request to access data;

determining whether at least a portion of the requested data is stored in the nonvolatile data store; and

accessing the requested data based on the step of determining.

12. The method of claim 11, wherein the step of accessing comprises:

if only a portion of the requested data is stored in the nonvolatile data store, then

flushing the portion of the requested data from the nonvolatile data store to the first data storage medium, and

accessing the requested data, including the portion flushed from the nonvolatile data store, from the first data storage medium.

13. A controller for a data storage system, the controller comprising:

a first interface for writing data to a first data storage device;

a second interface for writing data to a second data storage device comprising a solid-state nonvolatile data store;

a wear-leveling component configured to store a first portion of data to a first storage location in the nonvolatile data store and set a pointer to enable writing a second portion of data to a next storage location in the nonvolatile data store, the next storage location comprising an address of the nonvolatile data store that is sequentially after an address of the first storage location, wherein when the address of the first storage location is a last addressed location of the nonvolatile data store, the pointer is set to enable writing the second data to a first addressed location of the nonvolatile data store, and wherein the wear-leveling component is configured to flush the first portion of data stored in the nonvolatile data store to the first data storage device when a trigger occurs and preserve the pointer during the flush from the nonvolatile data store to the first data storage device such that the pointer enables writing the second data to the next storage location.

14. The controller of claim 13, wherein the trigger comprises at least one of an indication of a quantity of data stored in the nonvolatile data store, an indication that the pointer is set to a specific address, and an indication of a length of time from a previous writing of the nonvolatile data store to the first data storage device medium.

15. A data storage system comprising:

a data storage medium;

a non-volatile data store comprising solid-state memory having a plurality of storage locations addressed as a circular buffer; and

a controller configured to write data to sequential addresses in the circular buffer, wherein the controller stores a first portion of data to a first storage location in the circular buffer and sets a pointer to enable writing a second portion of data that is received to a next storage location in the circular buffer, and wherein the controller determines if an amount of data stored in the circular buffer is above a threshold and, in response, flushes the amount of data from a set of storage locations in the circular buffer, the controller preserving the pointer when the amount of data is flushed such that a next portion of data is stored to addresses in the circular buffer that are sequentially after the set of storage locations from which the amount of data was flushed.

16. The data storage system of claim 15, wherein the controller comprises a wear leveling component that is integrated with one or more of the non-volatile data store and a file system associated with the data storage system.

17. The data storage system of claim 16, wherein the wear leveling component is further configured to flush the amount of data from the non-volatile data store by retrieving the data from the circular buffer, sorting the data based on logical block addresses associated with the data, and storing the sorted data to the data storage medium based on the logical block addresses.

18. The data storage medium of claim 16, wherein the non-volatile data store comprises flash memory and the wear leveling component is integrated in a flash memory controller associated with the flash memory, and wherein the flash memory controller includes a flash translation layer having translation information for mapping logical addresses of data stored in the circular buffer with the corresponding physical addresses of the storage locations in the circular buffer where the data is stored.

19. The data storage system of claim 18, wherein the translation information comprises a B-tree structure having a plurality of nodes, each of the plurality of nodes including mapping information representing a portion of data stored in the circular buffer, the mapping information comprising:

a logical address associated with the portion of data;

a physical address identifying a location in the circular buffer where the portion of data is stored;

a size of the portion of data; and

at least one pointer that identifies a child node.

20. The data storage system of claim 16, wherein the wear leveling component is configured to receive a portion of data to be written to the data storage medium, determine whether the portion of data includes an amount of data above a threshold, and store the portion of data to sequential addresses in the circular buffer if the amount of data is below the threshold, wherein the portion of data is stored directly to the data storage medium if the amount of data is above the threshold.