In addition to manual snapshots, you can configure automatic snapshots according to the table
below. These snapshots are named ".auto-<timestamp>", and can be taken on half hourly, hourly,
daily, weekly, or monthly schedules. A schedule is a list of intervals and retention policies.
Times are displayed in the local (client browser) time zone. However, times are stored and
executed in UTC format and without regard to such conventions as daylight saving time. For example,
a snapshot scheduled for 10:00 a.m. PST (UTC-8) is stored and executed at 18:00 UTC.
Automatic snapshots can be set on a project or a share, but not both. Otherwise, overlapping
schedules and retention policies would make it impossible to guarantee both schedules. Removing an
interval, or changing its retention policy, will immediately destroy any automatic snapshots not
covered by the new schedule. Automatic snapshots with clones are ignored.
Previous versions of the software allowed for automatic snapshots at the frequency of a
minute. This proved to put undue strain on the system and was not generally useful. To help users
avoid placing undue stress on the system, this feature was removed with the 2010.Q3 release.
Snapshots can now only be specified at a period of once every half hour or longer.
Existing minute periods will be preserved should the software be rolled back, and previous instances
will expire according to the existing schedule, but no new snapshots will be taken. An alert will be
posted if a share or project with this frequency is found.
To add a new interval, click the
icon when viewing the "Schedules" tab. Each interval has the following
One of "half hour", "hour", "day", "week", or "month". This indicates how often the snapshot
This specifies an offset within the frequency. For example, when selecting an hour frequency,
snapshots can be taken at an explicit minute offset from the hour. For daily snapshots, the offset
can specify hour and minute, and for weekly or monthly snapshots the offset can specify day, hour,
Keep at most
Controls the retention policy for snapshots. Automatic snapshots can be kept forever (except
for half hour and hour snapshots, which are capped at 48 and 24, respectively) or can be limited to
a certain number. This limit will delete automatic snapshots for the given interval if they are
older than the retention policy. This is actually enforced by the time they were taken, not an
absolute count. So if you have hour snapshots and the ZFSSA is down for a day, when you come back up
all your hour snapshots will be deleted. Snapshots that are part of multiple intervals are only
destroyed when no interval specifies that they should be retained.