HP StorageWorks 4000s NAS 4000s and 9000s Administration Guide - Page 95

Shadow Copies user expectations of how many versions they will want to have available. End users might expect only a single shadow copy to be available, or they might expect three days or three weeks worth of shadow copies. The more shadow copies users expect, the more storage space administrators must allocate for storing them. Setting the limit too low also affects Backup and other backup programs that use shadow copy technology because these programs are also limited to using the amount of disk space specified by administrators. Note: Regardless of the volume space that is allocated for shadow copies, there is a maximum of 64 shadow copies for any volume. When the 65th shadow copy is taken, the oldest shadow copy is purged. The minimum amount of storage space that can be specified is 100 megabytes (MB). The default storage size is 10% of the source volume (the volume being copied). If the shadow copies are stored on a separate volume, change the default to reflect the space available on the storage volume instead of the source volume. Remember that when the storage limit is reached, older versions of the shadow copies are deleted and cannot be restored. When determining the amount of space to allocate for storing shadow copies, consider both the number and size of files that are being copied, as well as the frequency of changes between copies. For example, 100 files that only change monthly require less storage space than 10 files that change daily. 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. When using a basic disk as a storage area for shadow copies and converting the disk into a dynamic disk, it is important to take the following precaution to avoid data loss: ■ If the disk is a non-boot volume and is a different volume from where the original files reside, first dismount and take offline the volume containing the original files before converting the disk containing shadow copies to a dynamic disk. ■ The volume containing the original files must be brought back online within 20 minutes, otherwise, the data stored in the existing shadow copies is lost. ■ If the shadow copies are located on a boot volume, the disk to can be converted to dynamic without losing shadow copies. Note: Use the mountvol command with the /p option to dismount the volume and take it offline. Mount the volume and bring it online using the mountvol command or the Disk Management snap-in. NAS 4000s and 9000s Administration Guide 95