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

Concepts guide

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