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• Databases can be put into backup mode
• Databases can be taken offline
• A mount point can be unmounted
Only when this is carried out before a replica is consistent. However, if a database
is running on a filesystem or a rawdisk, there is no need to unmount the filesystem
or rawdisk as the database ensures that data is really written to the disk and not to
the filesystem cache.
For an online database backup, a raplica alone cannot be restored. The archive log
files from the application client are also needed. An archive log backup can be
started right after a split, when the database is taken out of backup mode.
The use of one replica in combination with the HP StorageWorks ContinuousAccess
XP technology to perform the backup does take away high availability of storage for
the duration of the backup. Additional mirrors retain full high availability of storage
and allow for the same backup approach.
The backup client can be a centralized backup client for multiple application clients
running different applications. In such cases, the backup client must run on the same
operating system as the application client, so as to access mirrored resources in a
native way.
The backup client should be capable of performing backups in a reasonable amount
of time. Though, theoretically, almost 24 hours may be required to perform a backup,
the restore time must be considered as well. It is thus recommended to have a backup
client that can perform the backup in 2 to 4 hours. It is recommended to perform the
restore through the application client.
In this approach the bulk of the data transfer happens via the backup client and its
access to the replica. The LAN connection between the backup client and application
client is only used to coordinate processes that are involved in the backup. There are
processes running on each client to allow the automation of the split.
Instant recovery
Data Protector instant recovery takes advantage of the split mirror technology to
provide instant data restore. The solution is based on zero downtime backup (ZDB)
solutions like the HP StorageWorks Disk Array XP integration, which uses split mirror
technology.
During a split mirror backup session, a replica is used for the purpose of moving the
data to a backup medium (tape). After a backup is completed, the replica can be
discarded and disk pair prepared for the next backup session by resynchronization,
or the replica can be left unchanged for the purpose of instant recovery. Several
replicas can exist at the same time. For example, HP StorageWorks Disk Array XP
Concepts guide 267