Shell commands

Take a snapshot of tableX called snapshotX

Snapshots can be taken while a table is disabled, or while a table is online and serving traffic.

• If a table is disabled (using disable <table>), an offline snapshot is taken. This snapshot is managed by the master and fully consistent with the state when the table was disabled. This is the simplest and safest method, but it involves a service interruption because the table must be disabled to take the snapshot.
• In an online snapshot, the table remains available while the snapshot is taken, and incurs minimal performance degradation of normal read/write loads. This snapshot is managed by the master and run on the RegionServers. The current implementation—simple-flush snapshots—provides no causal consistency guarantees. Despite this shortcoming, it offers the same degree of consistency as CopyTable and is a significant improvement.

Restore snapshot snapshotX (replaces the source table content)

For emergency use only.

Restoring a snapshot replaces the current version of a table with different version. To run this command, you must disable the target table. The restore command takes a snapshot of the table (appending a timestamp code), and then clones data into the original data and removes data not in the snapshot. If the operation succeeds, the target table is enabled.

List all available snapshots

List all available snapshots starting with ‘mysnapshot_’ (regular expression)

Remove a snapshot called snapshotX

Create a new table tableY from a snapshot snapshotX

Cloning a snapshot creates a new read/write table that serves the data kept at the time of the snapshot. The original table and the cloned table can be modified independently; new data written to one table does not show up on the other.