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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Chapter 2

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