Dell PowerVault DR6000 - Manual (Page 9)

9 Setting up NetVault Backup Native Virtual Tape Library on the Dell™ DR4X00 Disk Backup Appliance
1.4 Using and Managing a NetVault: Backup nVTL on DR4X00
appliance.
General guidelines and best practices for using a NVBU VTL on a DR4x00 unit:
 Only create enough media to cope with one full cycle of backups, and the relevant retention
policies.
 Set the “Automatically Label Blank Media” parameter to off to prevent erroneous use of blank
media and to ensure efficient use of available media within a tape pool. A tightly managed tape
pool will ease the space reclamation process.
 Pre-Labelling media and assigning a NVBU media Group Label will make the task of managing
tape pools much easier. Tapes will be re-used properly within a tape pool and space reclamation
can then be performed in an orderly fashion.
In our example NVBU VTL, we should now begin to look into grouping the data to be backed up to work
with media groups as target sets. For example, if we have 2 TB of data to backup, done on a weekly full
backup basis, with retention of 4 weeks, we will need 8 TB of media. With media at 100 GB each, 80
pieces of media can be added to the target media group. The main reason for using media groups is so
we can force the DR4x00 unit to re-use media before using blank media.
NVBU’s media selection algorithm is:
 Target media in a drive
 Target media in a slot
 Blank media
 Media marked for re-use.
As you can see blank media would be used before media marked for re-use. If we do not re-use media,
the DR4x00 unit will never be able to recover the space. By re-using media NVBU overwrites the previous
contents once the header has been updated and reuses available space which otherwise would not be
reclaimable by the DR4x00 clean cycle. Keeping spare media that is not grouped blank will keep the usage
of the DR4x00 unit as low as possible.
Because the Automatically Label Blank Media option is disabled, the backup may run out of media before
it completes, especially if the data set is growing. This is the trade off when using a DR4x00 unit, media
management become necessary to allow best use of the unit.
To alert administrators that a job has run out of media, NVBU’s Global Notification can be used to send an
email to the sys-op detailing that there is no suitable media to complete the job. The media request can
then be placed on hold in the Device Management window. Blank media can be added to the relevant
target media group and the media request taken off hold. While this is not ideal, it will allow the job to
complete.