Snapshot
During recovery, Sophia tries to read disk indexes. To reduce recovery time for big databases, Sophia periodically writes index dump to the disk generating a single snapshot file. This operation is called Snapshot.
Only indexes are saved during the operation, but database records remain untouched.
Snapshot period interval can be set or disabled using compaction.zone.snapshot_period variable.
/* take snapshot every 10 minutes */
sp_setint(env, "compaction.0.snapshot_period", 360);
Another important purpose of Snapshot is saving necessary statistic to distinct Hot and Cold node files used by Anti-Cache storage mode.