Configuring and Using Backup Devices

 

Device Concurrency, Segment Size, and Block Size

 

You can change the segment size in the Advanced Options dialog box of

 

a specific device. For detailed steps, refer to the online Help index

 

keyword “segment size”.

Changing the

Data Protector Media Agents and Disk Agents use memory buffers

Number of Buffers

during data transfer. Memory is divided into a number of buffer areas.

 

Values from 1 - 32 may be specified.

 

Each buffer area consists of 8 Disk Agent buffers, which are of the same

 

size as the block size configured for the device. The default device block

 

size is 64 KB.

 

You can change the number of buffers by changing the Advanced Option

 

properties of the selected drive. For detailed steps, refer to the online

 

Help index keyword “number of Disk Agent buffers”.

Block Size

When a device receives data, it processes it using a device-type-specific

 

(DDS, DLT) block size.

 

 

NOTE

Each backup device (drive) has a block size. A restore adjusts to block

 

size.

 

 

Before Changing

Data Protector uses a default device block size for each device type. The

Block Size in Data

block size applies to all devices created by Data Protector and to Media

Protector

Agents running on the different platforms.

 

The device block size is written on a media header so that Data Protector

 

knows the size to be used. If the device block size differs from the

 

medium’s block size, an error occurs.

 

You can change the device block size in the Data Protector GUI.

 

However, before changing the block size you need to check the supported

 

block size of the host adapter.

 

The minimum block size for old SCSI cards, such as the Adaptec 2940,

 

was 56 KB. Currently, the minimum block size that is mainly used with

 

newer SCSI cards is 64 KB.

 

You can increase the maximum block size on a Windows Media Agent

 

client by modifying its Registry. For information on how to modify the

 

block size, see the example in “Changing Block Size on Windows Media

 

Agent” on page A-51.

Chapter 2

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