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Configuring and Using Backup Devices
Device Concurrency, Segment Size, and Block Size
Chapter 278
Figure 2-14 Device Properties Dialog Box: Concurrency
Changing
Segment Size
Segment size is related to the size of data areas which Data Protector
uses in writing data to the media. It is user-configurable for each device.
Note that a smaller segment size consumes media space because each
segment has a file mark which takes up space on a medium. A larger
number of file marks results in faster restores, because the Media Agent
can quickly locate the segment containing the data to be restored.
Optimal segment size depends on the media type used in the device and
the kind of data to be backed up. The average number of segments per
tape is 50. The default segment size can be calculated by dividing the
native capacity of a tape by 50. The maximum catalog size is limited to a
fixed number (12 MB) for all media types.
Data Protector finishes a segment when the first limit is reached. When
backing up a large number of small files, the media catalog limit is
reached faster, which can result in smaller segment sizes.