Dell 740N Manual

A SERVICE OF

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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 20 MB from the file