Guidelines for Setting Mirror Schedules

Although MapR allows mirroring frequencies up to once per minute, setting a schedule at this frequency is not practical nor advisable. When you choose the mirror schedule, consider the amount of data on the volume and the load on the cluster. Remember that the mirroring frequency must allow enough time to complete one mirror operation before the next scheduled mirror operation starts. In addition, if you have a cascaded mirror setup (where A mirrors to B which mirrors to C), you cannot set a mirror schedule for C that starts before B finishes mirroring from A.

Warning: In general, you should not set a mirror schedule for more often than every 30 minutes.

If you set a mirror schedule to start mirroring before the previous mirror operation finishes, you will see an error message similar to this:

WARN Alarms [pool-2-thread-1]: Alarm raised: VOLUME_ALARM_MIRROR_FAILURE; Cluster: Cluster1; Volume: ; Message: Cannot start new scheduled mirror because existing mirror is in progress