Snapshot

• An implementation of writable snapshots.

• Makes a snapshot of the state of a device at a particular instant

• The first time each block is changed after that it makes a copy of the data prior to the change, so that it can reconstruct the state of the device.

• Run fsck on a snapshot of a mounted filesystem to test its integrity to find out whether the real device needs fsck or not.

• Test applications against production data by taking a snapshot and running tests against the snapshot, leaving the real data untouched.

• Take backups from a snapshot for consistency.