HP B6960-96035 User Manual download pdf (Page 279)

Instant recovery

During snapshot backup sessions, several snapshot copies of data can be produced

and can be retained on a disk array, each point-in-time copy in its own replica. The

retained snapshot copies of data can then be used for various purposes, such as

offline data processing or instant recovery. Only the point-in-time copies produced

during ZDB-to-disk and ZDB-to-disk+tape sessions can be restored using the instant

recovery functionality.

Using the instant recovery functionality, the point-in-time copy from a selected replica

is restored within a disk array and returned to its state at the point in time that the

snapshot data was produced. This process does not involve any restore of data from

tape media, dramatically reducing the overall restore time.

Application archive log files are not included in snapshot backup, therefore to restore

and apply them, they need to be restored from tape media.

Replica set and replica set rotation

The maximum number of replicas that can be kept concurrently on a disk array is

dependant on the disk array used. The replicas kept on the disk array for the same

backup specification form the replica set for that backup specification. The replica

set is defined by the maximum number of replicas that are to be kept on a disk array

for a particular backup specification. When during a snapshot backup session, this

number is reached, the snapshot data in the oldest replica in the replica set is

overwritten; if the number is not reached yet, a new replica is created - these two

actions are referred to as replica set rotation.

Types of snapshots

Depending on a disk array used, different types of snapshots can be created during

a Data Protector snapshot backup session. The Data Protector snapshot integrations

utilize the following types of snapshots:

• copy-on-write snapshots with the preallocation of disk space

• copy-on-write snapshots without the preallocation of disk space

• snapclones

Snapshots with the preallocation of disk space

The creation of copy-on-write snapshots with the preallocation of disk space requires

the same amount of disk capacity to be allocated as for the source volume. Data is

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HP B6960-96035 User Manual Page 279