HP ProLiant ML310 G3 Storage Server Administration Guide (WSS R2 version, March 2006)

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, star ting with the oldest shadow copies.
If defragmenting volumes on which shadow co pies are enabled, use a cluster (or alloca tion unit) size
of 16 KB or larger. Using this allocation unit size reduces the number of c opy outs occurring on the
snapshot. O therwise, 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 si ze of a volume, use the fsutil fsinfo ntfsinfo command. To change
the cluster size on a volume that contains data, back up the data on the volume, reformat it using
the new cluster size, and then restore the data.
Mounted drives
A mounted drive is a lo cal volume attached to an empty folder (c alled a mount point) on an NTFS
volume. When enabling shadow copies on a volume that contains mounted drives, the mounted drives
are not included when shadow copies are taken. In addition, if a mounted drive is shared and shadow
copies are enabled on it, users cannot access the shadow copies if they traverse from the host volume
(where the mount point is stored) to the mounted drive.
For example, assume there is a folder F:\data\users,andtheUsers folder is a mount point for G:\.
If shadow copies are enabled on both F:\ and G:\, F:\data is shared as \\server1\data,and
G:\data\users is shared as \\server1\users. In this ex ample, users can access pre vious versions of
\\server1\data and \\server1\users but not \\server1\data\users.
Managing shadow copies
The vssadmin tool provides a command line capability to create, list, resize, and delete volume shadow
copies.
The system administrator can make shadow copies available to end users through a feature c alled
“Shadow Copies for Shared Folders.” The administrator uses the Properties menu (see Figure 16)to
turn on the Shadow Copies feature, select the volumes to be co pied, and determine the frequency
with which shadow copies are made.
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