HP Data Protector Operations Guide

To copy a backup specification, right-click and chose Copy As…:
Using drive concurrency
The number of Disk Agents started for each Media Agent is called Disk Agent (backup)
concurrency and can be modified using the Advanced options for the device or when configuring
a backup.
Note: The concurrency set in the backup specification takes precedence over the concurrency set
in the device definition.
Data Protector provides a default number of Disk Agents that are sufficient for most cases. For
example, on a standard DDS device, two Disk Agents send enough data for the device to stream.
For library devices with multiple drives where each drive is controlled by one Media Agent, you
can set the concurrency for each drive independently.
If properly set, backup concurrency increases backup performance. For example, if you have a
library device with four drives, each controlled by a Media Agent and each Media Agent
receives data from two Disk Agents concurrently, data from eight disks is backed up
simultaneously.
You can concurrently back up parts of a disk to multiple devices. This method speeds up the
backup and is useful for backing up very large and fast disks to relatively slow devices. Multiple
Disk Agents read data from the disk in parallel and send the data to multiple Media Agents.
Note that concurrency can correspondingly decrease restore performance. If one mount point is
backed up through many Disk Agents, the data will be contained in multiple objects. To restore
the whole mount point you have to define all parts of the mount point in a single backup
specification and then restore the entire session.
When you back up large objects, you can speed up your backup by using multiple Disk Agents.
In the backup specification, you have to manually define which directories/files will be backed up
using a new Disk Agent. You should take care to avoid overlapping the same data.
If more than one Disk Agent is concurrently accessing the same disk, the performance of retrieving
data from the disk will drop. This can be different when using disk arrays.
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