HP B6960-90078 manual Device Concurrency, Segment Size, and Block, Streaming, Changing

Configuring and Using Backup Devices

Device Concurrency, Segment Size, and Block Size

	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	Data Protector provides a default number of Disk Agents that are
Concurrency	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”.

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