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Configuring and Using Backup Devices
Device Concurrency, Segment Size, and Block Size
Chapter 2 79
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
Number of Buffers
Data Protector Media Agents and Disk Agents use memory 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
Block Size in Data
Protector
Data Protector uses a default device block size for each device type. The
block size applies to all devices created by Data Protector and to Media
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.