9-14 Dell PowerVault 720N, 740N, and 760N System Administrator and Command Reference Guide
If you do not want the total amount of disk space consumed by all snapshots to
exceed a certain percentage of the used disk space, use the cumulative values in the
snap list output to determine which snapshots to delete. In the preceding exam-
ple, if you dont want more than 5% of used disk space to be spent by snapshots,
delete all snapshots listed below nightly.1 in the snap list output; that is, nightly.2,
nightly.3, and nightly.4. After deleting the snapshots, nightly.1 and all the other more
recent snapshots consume 5% of the used disk space.
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The snapshot reserve can be used only by snapshots, not by the active file system.
The default snapshot reserve is 20% of the available disk space. To change the
reserve, enter the following command:
snap reserve
volume_name

percent

For example:
snap reserve vol0 25
With no arguments, the snap reserve command displays the percentage of disk
space reserved for snapshots in each volume.
NOTE: Snapshots can exceed the snapshot reserve space.
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This section describes how to use the snap list output to determine which snap-
shot file to delete to free the most disk space.
In the sample snap list output in Displaying Snapshot Statistics, the cumulative
disk space used by snapshots gradually increases from top to bottom.
For example, in the %/used column, the cumulative space used by hourly.1 is 2% and
the cumulative space used by hourly.2 is 3%. This is not always the case.
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Consider a filer with a 100-MB file system that has not changed since the first snap-
shot was taken. The snap list command on this filer displays the following output:
%/used %/total date name
-------- --------- ------------ ---------
0% (0%) 0% (0%) May 05 16:00 hourly.0
0% (0%) 0% (0%) May 05 12:00 hourly.1
0% (0%) 0% (0%) May 05 08:00 hourly.2
The cumulative disk space used by snapshots does not increase because no changes
were made to the file system. However, if you had deleted 20MB from the file