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NOTE:
Some tape technologies place limitations on the number of file marks per medium. Ensure
that your segment size is not too low.
Figure 45 Data format
Segment size, measured in megabytes, is the maximum size of data segments. If you
back up a large number of small files, the actual segment size can be limited by the
maximum size of catalog segments. Segment size is user configurable for each device.
It affects the speed of a restore. A smaller segment size leaves less space on the
medium for data, because each segment has a file mark that takes up media space.
However, a larger number of file marks results in faster restores, because a Media
Agent can more quickly locate the segment containing the data to be restored.
Optimal segment size depends on the type of media used in the device and the kind
of data to be backed up. For example, by default the segment size for DLT medium
is 150 MB.
Block size
Segments are not written as a whole unit, but rather in smaller subunits called blocks.
The hardware of a device processes data in units of a device-type specific block size.
Data Protector allows you to adjust the size of the blocks it sends to the device. The
default block size value for all devices is 64 KB.
Media management and devices158