Methods of managing file allocation table information

• US 7,752,412 B2
• Filed: 09/29/2006
• Issued: 07/06/2010
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Tomlin, Andrew, Gorobets, Sergey Anatolievich
• Primary Examiner(s): PATEL, HETUL B
• Application Number:
  US11/537,243
• Publication Number:
  US 20080082774A1
• Time in Patent Office: 1,376 Days
• Field of Search: 711/103, 711/170
• US Class Current: 711/170
• CPC Class Codes: G06F 12/0238 Memory management in non-volatile memory, e.g. resistive RAM or ferroelectric memory

Abstract

In a nonvolatile memory system, a host allocates clusters and records allocation information in a File Allocation Table that is stored in the nonvolatile memory. A controller separately allocates certain data and records allocation in a record in a volatile memory. File Allocation Table information provided to the host is modified according to the record in the volatile memory.

Claims

1. A method of managing data in a nonvolatile memory array in which a host stores data, the host recording addresses of stored data in a File Allocation Table that is also stored in the nonvolatile memory array, comprising:

receiving a request from the host for a portion of the File Allocation Table that is stored in the nonvolatile memory array;

reading the portion of the File Allocation Table from the nonvolatile memory array;

subsequently modifying the portion of the File Allocation Table according to a record that indicates at least one address used by a memory controller to store data received from the host;

sending the modified portion of the File Allocation Table to the host; and

wherein the record is maintained in a volatile memory and is not maintained in the nonvolatile memory array.

2. The method of claim 1 wherein the nonvolatile memory array is not erasable.

3. The method of claim 1 wherein the record is a cluster map that includes an allocation/deallocation state for each of a plurality of clusters.

4. The method of claim 3 wherein the use of the address by the memory controller occurs in response to the host allocating data to a previously allocated cluster.

5. The method of claim 3 wherein the use of the address by the memory controller occurs in response to the host deallocating previously allocated clusters.

6. A method of managing data in a nonvolatile memory array comprising:

receiving a first portion of data from a host, the first portion of data allocated by the host to a first cluster that was previously allocated;

storing the first portion of data in the nonvolatile memory array;

receiving allocation information from the host, the allocation information linking the first portion of data and the first cluster, the allocation information indicating that a second cluster is available for storage of additional data;

storing the allocation information in the nonvolatile memory array;

subsequently, in response to a host request for the allocation information, reading the allocation information that indicates that the second cluster is available for storage of additional data from the nonvolatile memory array and subsequently modifying the allocation information according to a record, the modified allocation information indicating that the first cluster and the second cluster are both unavailable for storage of additional data;

subsequently sending the modified allocation information to the host in response to the host request; and

wherein the record is maintained in a volatile memory and is not maintained in the nonvolatile memory array.

7. A method of managing data in a nonvolatile memory in which a host allocates data in clusters and records the allocation in the nonvolatile memory, comprising:

generating a cluster map that indicates an allocation/deallocation state for each cluster of a plurality of clusters;

maintaining the cluster map in a volatile memory and not in the nonvolatile memory;

in response to receiving a host request for allocation information regarding the plurality of clusters, determining from the cluster map whether the plurality of clusters are allocated; and

if the plurality of clusters are not allocated, then generating allocation information from the cluster map and returning the generated allocation information to the host.

8. The method of claim 7 further comprising, if at least one of the plurality of clusters is allocated, then reading the allocation information from the nonvolatile memory.

9. The method of claim 8 further comprising modifying the read allocation according to the record and providing the modified allocation information to the host.

10. The method of claim 9 wherein the modified allocation information shows a file allocated to the at least one of the plurality of clusters.

11. A method of managing data in a nonvolatile memory system having a logical address space that is allocated to data stored in the nonvolatile memory, comprising:

recording allocation of address space by a host in a file system structure that is stored in the nonvolatile memory array;

recording allocation of address space that is not by the host in a record that is stored in a volatile memory array and is not stored in the nonvolatile memory array; and

in response to a host request for allocation data, consulting the record and providing a response to the host that is dependent on the contents of the record.

12. The method of claim 11 wherein the allocation of address space that is not by the host is allocation of address space for updating control data by a memory controller.

13. The method of claim 11 wherein the allocation of address space that is not by the host is allocation of address space by another host that does not record its allocation in the file system structure.

14. The method of claim 11 wherein the allocation of address space that is not by the host is allocation of address space by an embedded application within the nonvolatile memory system.

15. The method of claim 11 wherein the response includes an indication that a specific file is allocated to address space that is indicated by the record to be allocated.