HP StorageWorks 4000s NAS 4000s and 9000s Administration Guide - Page 97

Shadow Copies 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. 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 fsutil fsinfo ntfsinfo command. 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. Mounted Drives A mounted drive is a local volume attached to an empty folder (called 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 E:\data\users, and the Users folder is a mount point for F:\. If shadow copies are enabled on both E:\ and F:\, E:\data is shared as \\server1\data, and E:\data\users is shared as \\server1\users. In this example, users can access previous versions of \\server1\data and \\server1\users but not \\server1\data\users. NAS 4000s and 9000s Administration Guide 97