HP B6960-96035 User Manual download pdf (Page 159)

Increasing the block size can improve 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 using a different block size.

NOTE:

Use the same block size for media that can be used with different device types. Data

Protector can only append data to media using the same block size.

Number of disk agent buffers

Data Protector Media Agents and Disk Agents use memory buffers to hold data

waiting to be transferred. This memory is divided into a number of buffer areas (one

for each Disk Agent, depending on device concurrency). Each buffer area consists

of 8 Disk Agent buffers (of the same size as the block size configured for the device).

You can change this value to be anything between 1 and 32, although this is rarely

necessary. There are two basic reasons to change this setting:

• Shortage of memory

The shared memory required for a Media Agent can be calculated as follows:

DAConcurrency*NumberOfBuffers*BlockSize

Reducing the number of buffers from 8 to 4, for instance, results in a 50% reduction

in memory consumption, with performance implications.

• Streaming

If the available network bandwidth varies significantly during backup, then it

becomes more important that a Media Agent has enough data ready for writing

to keep the device in the streaming mode. In this case, increase the number of

buffers.

Device locking and lock names

Device names

When configuring devices for use with Data Protector, you can configure the same

physical device many times with different characteristics simply by configuring the

same physical device in Data Protector with different device names. For example, a

simple standalone DDS device can be configured as a compressed device and then

as an uncompressed device, although this is not recommended.

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HP B6960-96035 User Manual Page 159