Performing NDMP Backups
System Administration Manual
315
Note:
Devices will not be available or visible if they have not been enabled
through the SAN Management page.
NDMP and Snapshots
The Titan SiliconServer uses
snapshots
to backup data consistently and without being affected
by on-going file activity. Snapshots also facilitate incremental backups. However, it is also
possible to backup data without using snapshots.
Factors to Consider in the Backup Strategy
Snapshots and tape backups complement each other, and there is a strong case for using both
backup methods. The following are some factors to consider when designing a backup strategy.
❑
Backing up automatically created snapshots
When backing up a file system that is being actively updated, a snapshot of the file system is
much more likely to produce a fully consistent image than backing up the live file system. As a
result, NDMP is configured by default to automatically create a snapshot for backup.
❑
Backing up pre-created snapshots
A backup can be taken from a specific snapshot that has been created by rule or by user
request.
❑
To back up the latest snapshot created under a snapshot rule use the
NDMP_BLUEARC_USE_SNAPSHOT_RULE
environment variable (see
Supported
NDMP Environment Variables
).
❑
Alternatively, it is possible to request a specific snapshot by explicitly including
the snapshot name in the path to back up. Where the path is based on a CIFS
share name, indicate the snapshot with
/~snapshot/snapshot_name
; for paths
based on an NFS export name, use
/.snapshot/snapshot_name
instead. It is
also possible that the CIFS share or NFS export includes a snapshot name.
❑
Backing up databases and iSCSI Logical Units
Typically, special measures are needed when backing up files such as databases and iSCSI
Logical Units. The internal structures in these files are tightly coupled with the state of the
client software (database manager/iSCSI Initiator) that is controlling the files. Backing up the
file half way through a client operation may produce inconsistencies in the backup image that
would prevent the client using a recovery of the image. For this reason, any backup of the files
needs to ensure that files are in a consistent state when backed up. Snapshots can be used to
achieve this, see below for details. The most convenient mechanism is to use a snapshot rule as
this avoids having to explicitly specify the name of the snapshot used. However, it is important
to ensure that the backups created this way are not deleted too soon. If a snapshot being used
for a backup is deleted while the backup is still active then the backup will fail. For more
information on backing up and restoring iSCSI Logical Units, refer to the section
Backing Up
and Restoring iSCSI Logical Units
.
