A snapshot provides a consistent point-in-time image of a VxFS file system. A snapshot can be accessed as a read-only mounted file system to perform efficient online backups of the file system. Snapshots implement copy-on-write semantics that incrementally copy data blocks when they are overwritten on the snapped file system.
See the Veritas File System Administrator's Guide.
Snapshots for cluster file systems extend the same copy-on-write mechanism for the I/O originating from any node in the cluster.