Accelerated write performance

• US 20070050539A1
• Filed: 08/25/2005
• Published: 03/01/2007
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Pudipeddi, Ravisankar
• Granted Patent: US 7,779,207 B2
• Time in Patent Office: Days
• US Class Current: 711/113
• CPC Class Codes: G06F 11/1064 in cache or content addressable memories
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0638 Organizing or formatting or addressing of data
• CPC Class Codes: G06F 3/0671 In-line storage system

Abstract

A generic disk driver filter may be used to accelerate performance when writing to a disk. The generic disk driver filter may be connected between a file system and a disk driver and may be configured to be extensible and compatible with a variety of different file systems and different disk drivers. The generic disk driver filter has a filter component that intercepts and filters raw sector write commands from the file system before they are received by the disk driver. The generic disk driver filter may also have a cache memory component that stores a checksum for each sector which is written to the disk. The generic disk driver filter may also have a scavenger thread component that detects and removes latent checksum entries from the cache memory so as to preserve memory availability and reduce memory requirements.

Claims

1. A method for accelerating performance when writing a set of sectors to a disk comprising:

computing a checksum for each sector in the set of sectors;

comparing each computed checksum with a stored checksum for the corresponding sector;

identifying a contiguous sub-set of the set of contiguous sectors, each sector within the contiguous sub-set having a computed checksum that does not match its corresponding stored checksum; and

flushing the contiguous sub-set to the disk.

2. The method of claim 1, comprising flushing the contiguous sub-set to a flash media.

3. The method of claim 1, comprising computing a cyclic redundancy check checksum for each sector in the set of sectors.

4. The method of claim 1, wherein comparing each computed checksum with a stored checksum comprises determining that a computed checksum does not match a stored checksum if there is no stored checksum in memory for a corresponding sector.

5. The method of claim 1, further comprising:

identifying another contiguous sub-set of the set of contiguous sectors, each sector within the other contiguous sub-set having a computed checksum that does not match its corresponding stored checksum; and

flushing the other contiguous sub-set to the disk.

6. The method of claim 1, further comprising successfully completing the write if all of the sectors in the set of sectors have computed checksums that match their corresponding stored checksums.

7. The method of claim 1, further comprising storing the computed checksums in a cache memory.

8. The method of claim 7, further comprising deleting the computed checksums from the cache memory if the set of sectors is not rewritten to within a pre-determined time period.

9. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 1.

10. A system for accelerating performance when writing a set of sectors to a disk comprising:

a disk filter driver comprising;

a cache memory component that stores a checksum for each sector that has been written to the disk; and

a filter component that computes a checksum for each sector in the set of sectors, compares each computed checksum with a corresponding stored checksum from the cache memory, and flushes only sectors with non-matching stored and computed checksums to the disk.

11. The system of claim 10, wherein the disk filter driver is a generic disk filter driver that is compatible with a plurality of different file systems and a plurality of different disks.

12. The system of claim 10, wherein the disk filter driver is connected between a file system and a disk driver.

13. The system of claim 10, wherein the disk is a flash media.

14. The system of claim 10, wherein the stored checksums and the computed checksums are cyclic redundancy check checksums.

15. The system of claim 10, wherein the disk filter driver comprises a scavenger thread that releases the some of the stored checksums from the cache memory if their corresponding sectors have not been rewritten within a pre-determined time period.

16. The system of claim 10, wherein the disk filter driver cancels the write if all of the sectors in the set of sectors have matching stored and computed checksums.

17. A method for regulating a memory with a plurality of memory locations each for storing a sector checksum, each memory location having an associated use bit, the method comprising:

conducting a first pass in which a first value is assigned to all of the use bits;

assigning a second value to each use bit that is associated with a memory location to which a sector checksum is written;

conducting a second pass in which, for each use bit, it is determined whether the first value is still assigned to the use bit;

if the first value is still assigned to the use bit, then clearing the memory location associated with the use bit; and

if the first value is not still assigned to the use bit, then reassigning the first value to the use bit.

18. The method of claim 17, further comprising:

initiating a counting of a predetermined time period at the initiation of the first pass; and

initiating the second pass upon an expiration of the counting of the predetermined time period.

19. The method of claim 17, further comprising storing a region of sector checksums in a single memory location having an associated use bit.

20. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 17.