Determining Creation Frequency; Shadow Copies & Disk Defragmentation - Tandberg Data NAS Hardware Viking FS-1500 Administration Manual

Tandberg Data Shadow Copy Service
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4.2.4. Determining Creation Frequency

The more frequently shadow copies are created, the more likely that end
users will get the version that they want. However, with a maximum of 64
shadow copies per volume, there is a trade-off between the frequency of
making shadow copies and the amount of time that the earlier files will be
available.
By default, the NAS appliance will create shadow copies at 0700 and 1200,
Monday through Friday when the feature is enabled for a volume. However,
these settings are easily modified by the administrator so that the shadow
copy schedule can better accommodate end user needs. To modify these
schedules see the section on "Shadow Copy Schedules" documented later
in this chapter.
Note
The more shadow copies are created, the more disk space the shadow copies can
consume, especially if files change frequently.
4.2.4. Shadow Copies & Disk Defragmentation
When running Disk Defragmenter on a volume with shadow copies
activated, all or some of the shadow copies may be lost, starting with the
oldest shadow copies.
If defragmenting volumes on which shadow copies are enabled, use a
cluster (or allocation unit) size of 16 KB or larger. Utilizing this allocation unit
size reduces the number of copy outs occurring on the snapshot. Otherwise
the number of changes caused by the defragmentation process can cause
shadow copies to be deleted faster than expected. Note, however, that
NTFS compression is supported only if the cluster size is 4 KB or smaller.
Note
To check the cluster size of a volume, use the following text-mode command:
C:\>fsutil fsinfo ntfsinfo <volume pathname or drive letter>
To change the cluster size on a volume that contains data, backup the data on the
volume, reformat it using the new cluster size, and then restore the data.
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