Hp ProLiant SB460c SAN Gateway Storage Server User Manual download pdf (Page 33)

CAUTION:

To change the storage volume, shadow copies must be deleted. The existing file change history that is kept

on the original storage volume is lost. To avoid this problem, verify that the storage volume that is initially

selected is large enough.

Identifying the storage area

To store the shadow copies of another volume on the same file server, a volume can be dedicated

on separate disks. For example, if user files are stored on H:\, another volume such as S:\can be

used to store the shadow copies. Using a separate volume on separate disks provides better

performance and is recommended for heavily used storage servers.

If a separate volume will be used for the storage area (where shadow copies are stored), the maximum

size should be changed to No Limit to reflect the space available on the storage area volume instead

of the source volume (where the user files are stored).

Disk space for shadow copies can be allocated on either the same volume as the source files or a

different volume. There is a trade-off between ease of use and maintenance versus performance and

reliability that the system administrator must consider.

By keeping the shadow copy on the same volume, there is a potential gain in ease of setup and

maintenance; however, there may be a reduction in performance and reliability.

CAUTION:

If shadow copies are stored on the same volume as the user files, note that a burst of disk input/output

(I/O) can cause all shadow copies to be deleted. If the sudden deletion of shadow copies is unacceptable

to administrators or end users, it is best to use a separate volume on separate disks to store shadow copies.

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 storage server creates shadow copies at 0700 and 1200, Monday through Friday.

However, these settings are easily modified by the administrator so that the shadow copy schedule

can better accommodate end user needs.

Shadow copies and drive 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. Using 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.

HP ProLiant SB460c SAN Gateway Storage Server 33

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Hp ProLiant SB460c SAN Gateway Storage Server User Manual Page 33