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Performance and Sizing 37
Compressibility
The compressibility screen allows specification of the type of backup data. Tests have shown
that not all data can be compressed equally. The compression ratio will affect the amount of data
that can be stored on each tape cartridge, as well as the speed at which the tape drives can
read/write the data. If you have been performing tape backups on servers with DLT tape drives,
you should already have a good idea of the expected compression ratio for your data. Select the
type of data that most closely matches your environment, or enter this information in the Other
field. If your server has multiple types of data, select the anticipated composite average
compression ratio.
Figure 4-5. Data Compressibility Information screen
A compression ON/OFF check box allows you to calculate performance with Compression
turned off. For data sets with low compressibility, turning Compression OFF may increase
performance.
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