Reducing backup time

Selection list entries are processed serially for each client and in the order that they appear in the backup selections. A client can be added to multiple policies, to divide the client's files among the different backup selections lists. Multiple policies can reduce the backup time for that client because the files can be backed up in parallel.

Multiple clients can be backed up in parallel in the following situations:

Multiple storage devices are available (or if the policies are multiplexed).
The Maximum Jobs per Client Global host property, and the Limit Jobs per Policy policy attributes are set to allow it.

Note:

Understand disk and controller input and output limitations before configuring including a client in multiple policies. For example, if two file systems overload the client when backed up in parallel, place both file systems in the same policy. Schedule the file systems at different times or set Maximum Jobs per Client to 1.

Another method to reduce backup time is to select Allow Multiple Data Streams for a policy. Then, add NEW_STREAMS directives to the backup selections list.

For example:

	NEW_STREAM
	file_a
	file_b
	file_c
	NEW_STREAM
	file_d
	file_e
	file_f

The example produces two concurrent data streams. The first data string contains file_a, file_b, and file_c. The second data stream contains file_d, file_e, and file_f.

See Allow multiple data streams policy attribute.

Note:

For best performance, use only one data stream to back up each physical device on the client. Multiple concurrent streams from a single physical device can cause longer backup times. The disk heads must move back and forth between the tracks that contain files for the respective streams.

A directive instructs NetBackup to perform specific actions to process the files in the backup selections list.