Method and system for facilitating fast wake-up of a flash memory system

• US 20080177935A1
• Filed: 06/11/2007
• Published: 07/24/2008
• Est. Priority Date: 01/18/2007
• Status: Active Grant

• Current Assignee: Western Digital Israel Limited (Western Digital Corporation)
• Original Assignee: SanDisk IL Ltd. (Western Digital Corporation)
• Inventors: Lasser, Menahem, Avraham, Meir
• Granted Patent: US 7,769,945 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory

Abstract

Methods for maintaining data structures in accordance with the events of a nonvolatile memory system. At least part of one or more management tables and a future information data structure are stored in a nonvolatile memory. The future information data structure contains records of events expected to occur subsequent to the storing of the future information data structure. When flash memory events occur, those events are handled in accordance with the future information data structure. When the memory system wakes up, the management table(s) is/are retrieved and the records of the future information data structure are compared with the table(s) state. The table(s) is/are updated in accordance with the future information data structure.

Claims

1. A method of maintaining data structures of a memory system in accordance with events of the system, comprising the steps of:

(a) storing, in a nonvolatile memory of the memory system, at least a portion of a management table whose contents indicate a state of the memory system at a first point in time;

(b) storing in said nonvolatile memory a future information data structure including a plurality of records related to events of the memory system expected to occur subsequent to said storing of said future information data structure; and

(c) at a second point in time subsequent to said storing of said future information data structure, handling a said event in accordance with said future information data structure.

2. The method of claim 1, wherein said nonvolatile memory is a flash memory.

3. The method of claim 1, wherein said storing of said at least a portion of said management table includes updating said at least a portion of said management table in said nonvolatile memory.

4. The method of claim 3, wherein said storing of said at least a portion of said management table whose contents indicate said state of the memory system at said first point in time, also includes storing said at least a portion of said management table in a volatile memory, and wherein said updating is effected every N>

1 times that said management table is changed in said volatile memory.

5. The method of claim 3, wherein said updating is effected responsive to occurrences of selected said events.

6. The method of claim 3, wherein said updating is effected periodically.

7. The method of claim 3, wherein said updating is effected in accordance with availability of resources of the memory system.

8. The method of claim 1, wherein said future information data structure includes a list of blocks of said nonvolatile memory that are free at said first point in time.

9. A method of waking up a memory system, comprising the steps of:

(a) reading, from a nonvolatile memory of the memory system, at least a portion of a management table describing a state of the memory system at a point in time prior to the waking up;

(b) reading, from said nonvolatile memory, a future information data structure including a plurality of records related to events expected to occur subsequent to a storing of said future information data structure; and

(c) updating said management table in accordance with at least one record of said future information data structure.

10. The method of claim 9, wherein said nonvolatile memory is a flash memory.

11. The method of claim 9, wherein said updating changes said management table to describe a current state of the memory system.

12. The method of claim 9, wherein said updating is conditional.

13. The method of claim 12, further comprising the step of:

(d) inspecting said records to determine whether said state of the memory system has changed since said point in time, said updating then being conditional on said state of the memory system having changed since said point in time.