Working with Online Snapshots

Online snapshots are useful for verifying the contents of a snapshot. They can be generated either automatically or manually.

Note: It is recommended that you use VSS verified snapshots instead of manually creating an online, writable snapshot. Depending on the type of data on the volume, having VSS enabled is necessary to maintain recoverable data.

Certain backup utilities and data scanning utilities automatically create online snapshots. Normally these snapshots remain online only for the duration of the operation. If utility does not turn off the online feature after the process finishes, you should manually turn it off.

You should not use online, writable snapshots as a replacement for cloning. For example, you should not use online snapshots in the following situations:
  • Do not use online writable snapshots to add storage to a host by making it an extension of the existing file system.
  • If you plan to use a snapshot for testing or some situation where you need to use the snapshot as a regular volume. Instead, you should create a clone and use that a new volume and migrate data as needed.

Online, writable snapshots do not maintain point-in-time (PIT) information. If you change the data on an online snapshot, those changes will persist when the snapshot is turned offline. The changes to the upstream online snapshot will not replicate and the replica snapshot will only contain the data that was used to the create the original online snapshot.

If you create an online, unwritable snapshot, the data in the snapshot cannot be changed, so you do have a PIT snapshot.
NOTE: If you manually create an online snapshot and you make it non-writable, you cannot change it later to make it writable.