Virtual Media-How Many And What Size - Quantum DXi4700 User Manual

Chapter 1: System Description
Best Practices
The Data Deduplication license allows the DXi4700 to reduce the size of data stored on the system through
the deduplication process (see
Replication
The Replication license allows the DXi4700 to replicate data to up to two target systems and received
replicated data from up to ten source systems. (License key is pre-installed on all DXi4700 systems.)
Storage Capacity
The Storage Capacity license is factory-installed for the installed capacity. Additional capacity requires a
certificate license that comes with each Expansion module. This license allows the storage capacity of the
DXi4700 to be increased. (License key is pre-installed on all DXi4700 systems.)
OST
The OST license, when enabled, allows a Open Storage Technology (OST) connection. For Veritas users
with specific versions of the software, another replication option is available for DXi4700 models through the
Veritas OpenStorage (OST) API. (License Certificate is included with all DXi4700 NAS and Multi-Protocol
systems.)
Note: For more information, see the DXi-Series NetBackup and Backup Exec OST Configuration
Guide (6-67079).
Data-in-Flight Encryption
The Data-in-Flight Encryption license enables use of AES encryption (128-bit, 256-bit, or TLS with AES
256) when replicating data to another system. (Not available in all regions.)
Virtual Media—How Many and What Size?
There is no correct answer to this question as it really depends on your backup regime and the backup
application in use. A DXi system does not preallocate disk space when a virtual tape cartridge is created,
there can be an inclination to create a lot of large virtual tape cartridges, greater than the amount that is
actually required. While this has no initial bearing on the DXi's capacity utilization, it can cause issues down
the track.
Regarding the quantity of virtual media you need to create, as long as there is sufficient media to hold the
amount of backup data for the required retention period, the quantity does not really matter. However, it is
extremely important, as mentioned earlier, that the aging and expiry rules of the media pool are defined
early. If these rules are not defined, the virtual tape cartridges will never enter the scratch pool resulting in
you running out of virtual media, and in turn space on the DXi system. As a rule of thumb, more is better than
less; as long as expiry rules are defined.
Although there is no perfect size when it comes to creating virtual tape cartridges, there are a few factors to
consider. If a virtual tape cartridge is created at 200 GB, then it will be presented as storing 200 GB of native
data.
Creating smaller sized media is preferred, for example 50 GB or 100 GB, as it allows a virtual tape cartridge
to be completely filled even when backing up smaller data sets. Smaller sized media also aids the transfer of
data from virtual to physical tape platforms. Once again, virtual tape cartridge size will depend on the backup
application in use.
Quantum DXi4700 User's Guide
Data Reduction). (License key is pre-installed on all DXi4700 systems.)
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