Backup Retention controls how long recovery points will be retained on the device before being automatically purged. There are two modes of backup retention: Basic and Custom.
- Basic Retention mode will retain all snapshots for the specified number of days.
- Snapshots older than the selected time window will be removed from the system.
- Custom Retention mode retains all snapshots for a set number of days similar to Basic mode. Thereafter it will retain a set number of Daily, Weekly, Monthly, and Yearly The system will keep the LAST available snapshot for each period of time. (For example, the last snapshot of the day, week, month, or year).
- The value for Retain All Snapshots must be greater than 0 (Zero)
- Setting any retention period value to -1 indicates Keep Forever for that interval.
In the example settings presented in the image below, we have elected to keep all snapshot for 5 days.
After 5 days we will then begin keeping the last snapshot of the day for 5 days, the last snapshot of the week for 4 weeks, the last snapshot of the month for 3 months, and the last snapshot of the year forever.
Daily, Weekly, Monthly, and Yearly retention may overlap. Overlapping snapshots are not deleted until they are no longer valid for any retention Interval. (For example, the last snapshot of the day on December 31 is both a monthly and a yearly and will not be deleted until it is beyond both the “Monthly” and “Yearly” retention intervals.)
- For example, suppose that it is 1:00PM on Thursday, January 8th. In this case, we would have all snapshots taken from 12:00am on Saturday, January 3rd up to the present time (keep all for 5 days)
- The last snapshot of each day taken on Monday, December 29th through Friday, January 2nd (Keep 5 Daily’s).
- Our most recent Weekly would be the last snapshot of the day taken on Sunday, December 28th
- We would also have Weekly snapshots from December 28th, 21st, and 14th.
- Our Monthly snapshots would be the last snapshot of the day taken on December 31st, November 30th, and October 31st.
- Finally, our Yearly snapshots would be the last snapshot of the day taken on December 31st of each year that we have had the Appliance in operation. Not that this overlaps with our most recent Monthly.
Note that ALL of our intervals begin on the same day, after the keep-all-snapshots date. For example, if you elect to keep 14 daily snapshots, two of those snapshots will overlap with the first two weekly snapshots.
If no snapshot exists for any of the given days listed above, the next most recent snapshot within the time interval will be chosen. For example, if no snapshots exist on Saturday or Sunday, the last snapshot taken on Friday will be selected for the Weekly, and so on.