File system with per-extent checksums

Patent metadata

Field	Value
Publication number	US-2016092467-A1
Application number	US-201414501922-A
Country	US
Kind code	A1
Filing date	Sep 30, 2014
Priority date	Sep 30, 2014
Publication date	Mar 31, 2016
Grant date	—

Abstract

A file system allows a different checksum algorithm to be used for different extents of a file system object independently of other extents of the file system object. The checksum algorithm can be a selectable attribute of an extent or range of extents of a file system object, such that some extents of a file system object can use a first checksum algorithm, while other extents of the file system object can use a second checksum algorithm. An extent of the file system object also may have no associated checksum algorithm. The file system stores, for each extent of a file system object, data indicating a checksum for the extent and an indication of any checksum algorithm used for the extent.

First claim

What is claimed is:

1 . A computer with a file system for managing storage of and access to a plurality of file system objects on one or more storage devices, comprising:
a storage medium storing data including, for different extents of a file system object, an indication of checksum algorithm applied to the extents from among a plurality of different checksum algorithms and a checksum value for each of the different extents that store data and have the different checksum algorithms applied.

2 . The computer of claim 1 , wherein the file system, in response to a write operation to an extent of a file system object, identifies a checksum algorithm to apply to the extent, computes a checksum value for the extent using the checksum algorithm, and stores an indication of the checksum algorithm and the checksum value associated with the extent.

3 . The computer of claim 1 , wherein the file system, in response to a read operation for an extent of a file system object, identifies a checksum algorithm applied to the extent, computes a checksum value for data read from storage for the extent using the checksum algorithm, and compares the computed checksum value to a stored checksum value for the extent.

4 . The computer of claim 1 , wherein the file system, in response to an operation to change a checksum algorithm applied to an extent of a file, a file system computes a checksum value for data read from storage for the extent using the checksum algorithm, and stores an indication of the checksum algorithm and the checksum value associated with the extent.

5 . The computer of claim 1 , wherein the indicator of the checksum algorithm is a checksum indicator stored in an entry for the extent in an extent table for the file system object.

6 . The computer of claim 5 , wherein the checksum value for an extent is stored in an entry for the extent in an extent table for the file system object.

7 . The computer of claim 1 , wherein the indicator of the checksum algorithm is a checksum indicator for an extent accessed indirectly through an entry for the extent in the extent table for the file system object.

8 . The computer of claim 7 , wherein the checksum value for an extent is accessed indirectly through an entry for the extent in the extent table for the file system object.

9 . The computer of claim 1 , wherein the indicator of the checksum algorithm is a checksum indicator for an extent stored in association with data about the storage location of stored data for the extent.

10 . The computer of claim 1 , wherein the checksum value for an extent of a file system object is stored in association with data about the storage location of stored data for the extent.

11 . A computer-implemented process performed by a file system of a computer, comprising:
receiving an indication of checksum algorithm applied to an extent, from among a plurality of different checksum algorithms, and applying the checksum algorithm to stored data for the extent independently of other extents of the file system object.

12 . The computer-implemented process of claim 11 , further comprising, in response to a write operation to an extent of a file system object:
identifying a checksum algorithm to apply to the extent, computing a checksum value for the extent using the checksum algorithm, and storing an indication of the checksum algorithm and the checksum value associated with the extent.

13 . The computer-implemented process of claim 11 , further comprising, in response to a read operation for an extent of a file system object:
identifying a checksum algorithm applied to the extent, computing a checksum value for data read from storage for the extent using the checksum algorithm, and comparing the computed checksum value to a stored checksum value for the extent.

14 . The computer-implemented process of claim 11 , further comprising, in response to an operation to change a checksum algorithm applied to extents of a file,
computing a checksum value for data read from storage for the extent using the checksum algorithm, and storing an indication of the checksum algorithm and the checksum value associated with the extent.

15 . The computer-implemented process of claim 11 , wherein the indicator of the checksum algorithm is a checksum indicator stored in an entry for the extent in an extent table for the file system object, and wherein the checksum value for an extent is stored in an entry for the extent in an extent table for the file system object.

16 . An article of manufacture includes a storage medium, with computer program code stored in the storage medium that, when executed by one or more computers, configures the one or more computers to:
receive an indication of checksum algorithm applied to an extent, from among a plurality of different checksum algorithms, and apply the checksum algorithm to stored data for the extent independently of other extents of the file system object.

17 . The article of manufacture of claim 16 , wherein the one or more computers are configured to, in response to a write operation to an extent of a file system object:
identifying a checksum algorithm to apply to the extent, computing a checksum value for the extent using the checksum algorithm, and storing an indication of the checksum algorithm and the checksum value associated with the extent.

18 . The article of manufacture of claim 16 , the one or more computers are configured to, in response to a read operation for an extent of a file system object:
identifying a checksum algorithm applied to the extent, computing a checksum value for data read from storage for the extent using the checksum algorithm, and comparing the computed checksum value to a stored checksum value for the extent.

19 . The article of manufacture of claim 16 , the one or more computers are configured to, in response to an operation to change a checksum algorithm applied to extents of a file,
computing a checksum value for data read from storage for the extent using the checksum algorithm, and storing an indication of the checksum algorithm and the checksum value associated with the extent.

20 . The article of manufacture of claim 16 , wherein the indicator of the checksum algorithm is a checksum indicator stored in an entry for the extent in an extent table for the file system object, and wherein the checksum value for an extent is stored in an entry for the extent in an extent table for the file system object.

Assignees

• Microsoft Corp

Inventors

• Lee Chesong
• Das Raj
• Rat Cornel
• Tipton William

Classifications

• G06F16/183 Primary

  Provision of network file services by network file servers, e.g. by using NFS, CIFS (network file access protocols H04L67/1097) · CPC title

• G06F11/1004 Primary

  to protect a block of data words, e.g. CRC or checksum (G06F11/1076 takes precedence; security arrangements for protecting computers or computer systems against unauthorized activity G06F21/00) · CPC title

• G06F16/122

  using management policies (point-in-time backing up or restoration of persistent data G06F11/1446; file migration policies for HSM systems G06F16/185) · CPC title

• G06F17/30203 Primary

  Physics · mapped topic

• G06F17/30082

  Physics · mapped topic