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Configuring and Using Backup Devices
Device Concurrency, Segment Size, and Block Size
Chapter 276
Device Concurrency, Segment Size, and Block
Size
Streaming To maximize a device’s performance, it has to 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 more data, reverses the tape a little and resumes writing to the
tape, and so on. In other words, if the data rate written to the tape is less
than or equal to the data rate which can be delivered to the device by the
computer system, the device is streaming. Device streaming is also
dependent on other factors such as network load and the block size of the
data written to the backup device in one operation.
For additional information on device concurrency, segment size, and
block size, see the Media Management chapter in the HP OpenView
Storage Data Protector Concepts Guide.
Changing
Concurrency
Data Protector provides a default number of Disk Agents that are
started for each device. Increasing the number of Disk Agents sending
data to a Media Agent at the same time improves device streaming.
In the Advanced Options dialog box of a specific device, set the
Concurrency to the maximum number of Disk Agents allowed to feed
data to each Media Agent. See Figure 2-13 on page 77. For detailed steps,
refer to the online Help index keyword “concurrency”.
Concurrency can also be set in the backup specification. The concurrency
set in the backup specification will take precedence over the concurrency
set in the device definition. See Figure 2-14 on page 78. For detailed
steps, refer to the online Help index keyword “concurrency”.