Creating a snapshot

Use the mmcrsnapshot command to create a snapshot of an entire GPFS file system at a single point in time. Snapshots appear in the file system tree as hidden subdirectories of the root.

Global snapshots appear in a subdirectory in the root directory of the file system, whose default name is .snapshots. If you prefer to access snapshots from each directory rather than traversing through the root directory, then you can use an invisible directory to make the connection by issuing the mmsnapdir command. For more information, see Linking to a snapshot.

A snapshot of the file system, Device, is identified by a SnapshotName name on the mmcrsnapshot command. For example, given the file system fs1 to create a snapshot snap1, enter: 
mmcrsnapshot fs1 snap1
The output is similar to this: 
Writing dirty data to disk.
Quiescing all file system operations.
Writing dirty data to disk again.
Snapshot snap1 created with id 1.
Before issuing the command, the directory structure would appear similar to: 
/fs1/file1
/fs1/userA/file2
/fs1/userA/file3
After the command is issued, the directory structure would appear similar to: 
/fs1/file1
/fs1/userA/file2
/fs1/userA/file3

/fs1/.snapshots/snap1/file1
/fs1/.snapshots/snap1/userA/file2
/fs1/.snapshots/snap1/userA/file3
If a second snapshot is supposed to be created later, then the first snapshot would remain as it is. A snapshot can be made only of an active file system, not of an existing snapshot. The following command creates another snapshot of the same file system: 
mmcrsnapshot fs1 snap2
The output is similar to this: 
Writing dirty data to disk.
Quiescing all file system operations.
Writing dirty data to disk again.
Snapshot snap2 created with id 2.
After the command is issued, the directory structure would appear similar to: 
/fs1/file1
/fs1/userA/file2
/fs1/userA/file3

/fs1/.snapshots/snap1/file1
/fs1/.snapshots/snap1/userA/file2
/fs1/.snapshots/snap1/userA/file3

/fs1/.snapshots/snap2/file1
/fs1/.snapshots/snap2/userA/file2
/fs1/.snapshots/snap2/userA/file3

For more information, see the mmcrsnapshot command.