Peer snapshot -psnap
The peer snapshot function provides a snapshot at home and cache separately, ensuring application consistency on both sides (cache and home).
When you take a peer snapshot, it creates a snapshot in the cache fileset then queues a snapshot to be executed at the home. When all of the queued requests outstanding at the time the snap was performed in cache have been flushed to the home fileset so that the home data is consistent with cache, a snapshot of the corresponding home fileset is performed. The result is a pair of peer snapshots, one at the cache and one at the home. Both refer to the same copy.
If the cache fileset is disconnected from the home fileset when the cache snapshot is created, the cache records that the peer snapshot on the home fileset has not been created. When connection is restored, it attempts to create the snapshot.
Peer snapshots are not allowed on a SW cache that uses the NSD protocol for communicating with home.
- To create a fileset level snapshot in cache of a single-writer fileset called sw in file system
fs1, run the following command:
mmpsnap fs1 create -j sw
The system displays the following output:
Writing dirty data to disk. Quiescing all file system operations. Writing dirty data to disk again. Snapshot psnap-13882361812785649740-C0A80E85:4F44B305-59-12-03-01-02-27-28 created with id 8. Snapshot psnap-13882361812785649740-C0A80E85:4F44B305-59-12-03-01-02-27-28 created at the satellite. Core snapshot has been queued.
- To view the snapshot, run the following command:
mmlssnapshot fs1 -j sw
The system displays the following output:
Snapshots in file system fs1: Directory SnapId Status Created Fileset psnap-13882361812785649740-C0A80E85:4F44B305-59-12-03-01-02-27-28 8 Valid Thu Oct 27 02:27:29 2016 sw
- To view the snapshot at home, run the following command at home.:
mmlssnapshot fs1
The system displays the following output:
Snapshots in file system fs1: Directory SnapId Status Created Fileset psnap-13882361812785649740-C0A80E85:4F44B305-59-12-03-01-02-27-28 8 Valid Thu Oct 27 02:23:16 2016