The result of a successful backup session with object mirroring is one media set containing the backed up objects and additional media sets containing the mirrored objects. The mirrored objects on these media sets are treated as object copies.

Benefits of object mirroring

The use of the object mirror functionality serves the following purposes:

•It increases the availability of backed up data due to the existence of multiple copies.

•It enables easy multi-site vaulting, as the backed up data can be mirrored to remote sites.

•It improves the fault tolerance of backups, as the same data is written to several media. A media failure on one medium does not affect the creation of the other mirrors.

Object mirror operation

In a backup session with object mirroring, each selected object is backed up and at the same time mirrored as many times as specified in the backup specification. See Figure 35 on page 121.

Let us take Object 3 in the figure as an example. The Disk Agent reads a block of data from the disk and sends it to the Media Agent that is responsible for the backup of the object. This Media Agent then writes the data to the medium in Drive 2 and forwards it to the Media Agent that is responsible for mirror 1. This Media Agent in turn writes the data to the medium in Drive 4 and forwards it to the Media Agent that is responsible for mirror 2. This Media Agent writes the data to the medium in Drive 5. At the end of the session, Object 3 is available on three media.

120

Planning your backup strategy