Specifies the number of weekly, nightly, and hourly snapshots to keep on the filer.
The following list describes the default values for when the different snapshots are taken:
Weekly snapshots are taken at 24:00 on Sunday, creating snapshots called weekly.n, where n is an integer (weekly.0, weekly.1, weekly.2, and so on).
Nightly snapshots are taken at 24:00 Monday through Saturday, creating snapshots called nightly.n, where n is an integer (nightly.0, nightly.1, and so on).
Four hourly snapshots are taken at 8 a.m., noon, 4 p.m., and 8 p.m., unless specified otherwise using the hourly snapshot schedule in this window, creating snapshots called hourly.n, where n is an integer (hourly.0, hourly.1, hourly.2, and so on).
The filer creates only one snapshot at a time. For example, when it is creating the weekly snapshot at 24:00 on Sunday, it does not create the hourly or nightly snapshot at that time.
By default, Data ONTAP retains the two most recent nightly snapshots and the six most recent hourly snapshots, and deletes the oldest nightly and hourly snapshots when new snapshots are created. The following guidelines provide information about how to decide the number of snapshots to keep:
If users rarely lose files or typically notice lost files right away, use the default snapshot schedule.
If users commonly lose files and need to restore them, delete the snapshots less often than specified by the default schedule.
For file systems that change very quickly, reduce the number of snapshots scheduled. For example, if the entire file system on a filer is filled and emptied each day (for example, a file system storing large temporary files for a CAD application), it might not be appropriate to use daily or weekly snapshots. On a very active system, schedule snapshots every hour and keep them for just a few hours.