Taking a snapshot

Steps for taking a global snapshot or per node.

Snapshots are taken per node using the nodetool snapshot command. To take a global snapshot, run the nodetool snapshot command with a parallel ssh utility, such as pssh.

A snapshot first flushes all in-memory writes to disk, then makes a hard link of the SSTable files for each keyspace. You must have enough free disk space on the node to accommodate making snapshots of your data files. A single snapshot requires little disk space. However, snapshots can cause your disk usage to grow more quickly over time because a snapshot prevents old obsolete data files from being deleted. After the snapshot is complete, you can move the backup files to another location if needed, or you can leave them in place.
Note: Restoring from a snapshot requires the table schema.

Procedure

  1. Run nodetool cleanup to ensure that invalid replicas are removed.
    nodetool cleanup cycling
  2. Run the nodetool snapshot command, specifying the hostname, JMX port, and keyspace. For example:
    nodetool snapshot -t cycling_2017-3-9 cycling

Results

The name of the snapshot directory appears:
Requested creating snapshot(s) for [cycling] with snapshot name [2015.07.17]
Snapshot directory: cycling_2017-3-9
The snapshot files are created in data/keyspace_name/table_name-UUID/snapshots/snapshot_name directory.
ls -1 data/cycling/cyclist_name-9e516080f30811e689e40725f37c761d/snapshots/cycling_2017-3-9

For all installations, the default location of the data directory is /var/lib/cassandra/data.

The data files extension is .db and the full CQL to create the table is in the schema.cql file.
manifest.json
mc-1-big-CompressionInfo.db
mc-1-big-Data.db
mc-1-big-Digest.crc32
mc-1-big-Filter.db
mc-1-big-Index.db
mc-1-big-Statistics.db
mc-1-big-Summary.db
mc-1-big-TOC.txt
schema.cql