Tape Drive Compression and what controls it. (4047980)

Backup data is not being compressed on to Media. Native capacity is used. Compression of this data to the media does not appear to be working.

There seems to be some confusion on who/what controls compression on a tape drive.
NetVault does not do the compression. This is all done by the tape devices.

Tape devices come with compression built in. It is usually 90% of the time enabled by default.

If you experience data sent to tape media that is not compressed it is because the drive is not compressing the data. It is either not enabled on the drive or the drive itself and/or firmware is malfunctioning.

Control of data compression is handled with the Tape drive itself. Any failures to compress data would be related to the type of Media being used, or problems with the Tape device and/or firmware itself.
 

Furthermore, not all data compress at the same ratio. The compression ratio achieved is affect by many factors including :

type of data

Location of data

Quality of media used

Quality of the tape drive