Tandberg Data NAS Hardware Viking FS-1500 - Manual (Page 41)

Tandberg Data Shadow Copy Service
__________________________________________________________________________________________________
4-3 Tandberg Viking Series Storage Server Administration Manual
4.2.2. Allocating Disk Space
When shadow copies are enabled on a volume, the maximum amount of
volume space to be used for the shadow copies can be specified. The
default limit is 10 percent of the source volume (the volume being copied).
The limit for volumes in which users frequently change files should be
increased. Also, note that setting the limit too low causes the oldest shadow
copies to be deleted frequently, which defeats the purpose of shadow copies
and frustrates users.
If the frequency of changes to each file is greater than the amount of space
allocated to storing shadow copies, then no shadow copy is created.
Therefore, administrators should carefully consider the amount of disk space
they want to set aside for shadow copies, and keep in mind 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.