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There are three main methods for restoring data from a snapshot:
Copying a file from a snapshot duplicates that file, which roughly doubles the amount of storage space it consumes. Even if the original file is deleted from HEAD, the copy of that file will remain in the snapshot.
Cloning a file from a snapshot also duplicates that file. However, unlike a copy, a clone does not consume any additional space on the cluster, unless either the clone or original file is modified. File cloning is covered in more detail towards the end of this paper.
However, the most efficient of these approaches is the SnapRevert job, which automates the restoration of an entire snapshot to its top-level directory. This is invaluable for quickly reverting to a previous, known-good recovery point, for example, if a virus or malware outbreak occurs. The SnapRevert job can be run from the Job Engine WebUI, and requires adding the wanted snapshot ID.
Figure 14. Running a snapshot revert job
Before a snapshot is reverted, SnapshotIQ creates a snapshot of the data that is being replaced. This enables the snapshot revert action to be undone later, if necessary.
Also, individual files, rather than entire snapshots, can also be restored in place using the isi_file_revert command-line utility. This can help drastically simplify virtual machine management and recovery.