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Further Information
Performance Considerations
Appendix AA-10
• Load Balancing: This is where Data Protector dynamically
determines which filesystem should be backed up to which device.
Normally, it is best to enable this feature. This is especially true
when a large number of filesystems in a dynamic environment are
being backed up.
Configuring Backups and Restores
Any given infrastructure must be used efficiently in order to maximize
performance. Data Protector offers high flexibility in order to adapt to
the environment.
Device Streaming
To maximize a device’s performance, it must be kept streaming. A device
is streaming if it can feed enough data to the medium to keep it moving
forward continuously. Otherwise, the tape has to be stopped, the device
waits for some more data, reverses the tape a little and resumes to write
to the tape, and so on. In other words, if the data rate written to the tape
is less or equal the data rate which can be delivered to the device by the
computer system, then the device is streaming. In network-focused
backup infrastructures, this deserves attention.
Backups can be setup so that the data from several disk agents is sent to
one Media Agent, which sends the data to the device.
Block Size
The device hardware processes data it receives using a device type
specific block size. Data Protector allows to adjust the size of the block it
sends to the device. The default value is 64kB.
Increasing the block size can improve the performance. Changing the
block size should be done before formatting tapes. For example, a tape
written with the default block size cannot be appended to a tape using a
different block size.
Software Compression
Software compression is done by the client CPU when reading the data
from the disk. This reduces the data which gets send over the network,
but it requires significant CPU resources from the client.