Selection of devices

You need separate devices to be used with the source media and the target media. The destination devices can have a larger block size than the source devices. However, to avoid impact on performance, it is recommended that the devices have the same block size and are connected to the same system or to a SAN environment.

Object copying is load balanced by default. Data Protector makes optimum use of the available devices by utilizing as many devices as possible.

If you do not specify the source devices to be used in the object copy specification, Data Protector uses the default devices. By default, the devices that were used for writing the objects are used as source devices. If destination devices are not specified per object, Data Protector selects them automatically from those you selected in the object copy specification according to the following criteria in the order of priority:

•destination devices of the same block size as source devices are selected before those with a different block size

•locally attached devices are selected before network attached devices

Devices are locked at the beginning of the session. Devices that are not available at that time cannot be used in the session, as device locking after the beginning of the session is not possible. If a media error occurs, the device with errors will be avoided within that copy session.

Selection of the media set to copy from

If an object version that you want to copy exists on more than one media set, which has been created using one of the Data Protector data duplication methods, any of the media sets can be used as a source for copying. You can influence the media set selection by specifying the media location priority.

The overall process of media selection is the same as for restore. For details, see “Selection of the media set” on page 126.

Object copy session performance

An impact on object copy performance can be caused by factors such as device block sizes and the connection of devices. If the devices used in the object copy session have different block sizes, the data will be repackaged during the session, which takes additional time and resources. If the data is transferred over the network, there will be additional network load and time consumption. This impact can be minimized if the operation is load balanced.

Concepts guide

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