Instant snapshot
AssigneeNetwork Appliance, Inc.
InventorsBlake Lewis, John K. Edwards, Srinivasan Viswanathan
Life of this patent
Estimating the term…
Abstract
An improved method and apparatus for creating a snapshot of a file system. A record of which blocks are being used by a snapshot is included in the snapshot itself, allowing effectively instantaneous snapshot creation and deletion. The state of the active file system is described by a set of metafiles; in particular, a bitmap (henceforth the “active map”) describes which blocks are free and which are in use. The inode file describes which blocks are used by each file, including the metafiles. The inode file itself is described by a special root inode, also known as the “fsinfo block”. The system begins creating a new snapshot by making a copy of the root inode. This copy of the root inode becomes the root of the snapshot.
Claims27
A method of capturing the contents of files and directories in a file system, said file system comprising a set of storage blocks for plural files in a mass storage system including steps of
- recording an active map in said file system of said storage blocks used by said plural files in said active file system;
- recording a consistency point in said file system including a consistent version of said plural files in said file system at a previous time, said consistency point including a copy of said active map at said previous time;
- refraining from writing data to storage blocks in response to said active map and at least one said copy of said active map included in said consistency point;
- and
- generating a summary map by performing a logical OR operation with at least one said copy of said active map included in said consistency point.
A file system comprising:
- a set of storage blocks for plural files in a mass storage system;
- an active map in said file system of said storage blocks used by said plural files in said active file system;
- and
- a consistency point recorded in said file system, said consistency point including a consistent version of said plural files in said file system at a previous time and a copy of said active map at said previous time;
- wherein said file system refrains from writing data to storage blocks in response to said active map and at least one said copy of said active map included in said consistency point;
- and
- wherein said file system generates a summary map by performing a logical OR operation with at least one said copy of said active map included in said consistency point.
A memory storing information including instructions, the instructions executable by a processor to capture the contents of files and directories in a file system, said file system comprising a set of storage blocks for plural files in a mass storage system, the instructions comprising the steps of:
- (a) recording an active map in said file system of said storage blocks used by said plural files in said active file system, (b) recording a consistency point in said file system including a consistent version of said plural files in said file system at a previous time, said consistency point including a copy of said active map at said previous time, (c) refraining from writing data to storage blocks in response to said active map and at least one said copy of said active map included in said consistency point, and (d) generating a summary map by performing a logical OR operation with at least one said copy of said active map included in said consistency point.
Dependencies are inferred from the claim text.