Snapshots 9-11
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Quotas do not count disk space consumed by snapshots. If snapshots were included
in the quota calculations, users could end up in a state where they could not create
any new files until all snapshots containing their old files expired.
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This section describes
how to schedule snapshots to suit your environment
how to determine a reasonable snapshot reserve
how to adjust the amount of space snapshots use
The examples in this section are for a volume named home.
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The best way to manage the amount of space consumed by snapshots in each vol-
ume is to use the snap sched command to adjust the schedule of snapshot
creation.
Following are some suggested strategies for scheduling and retaining snapshots:
If users rarely lose files or typically notice lost files right away, use the default
snapshot schedule. For example, this is the schedule that creates a snapshot
every day and keeps two:
snap sched home 0 2 6@8,12,16,20
If users commonly lose files and need to restore them, Dell recommends that
you delete the snapshots less often than you would in the preceding example.
On many systems only 5% or 10% of the data changes each week, so the
snapshot schedule of six nightly and two weekly snapshots consumes 10% to
20% of disk space. Considering the benefits of snapshots, it is worthwhile to
reserve this amount of disk space for snapshots. Following is the recommended
snapshot schedule, which keeps six daily snapshots and two weekly snapshots:
snap sched home 2 6 8@8,12,16,20