Dat40i, DDS4 and media full after 18Gb with Novell and Arcserve

[Eddie Hager]

We have a half year old DAT40i in a Novell 4.11 server and Arcserve 7.0. When I make a backup of two servers, I get a media full warning when 18Gb of data is written to tape, where I should be able to write 20-40Gb of data to a DDS4 tape.
When I switch the hardware compression off in Arcserve, the amount of data written to tape is the same. I have checked the dipswitch settings. I have tried another backupunit in another server that has the same configuration. The data that is written to tape is not compressed (no ghost-files etc.). I have used different tapes.
Can anybody help me out with this?

[Steve W]

If you can boot a Windows O/S, try running the compression test within HP Library & Tape Tools. You can download it from
http://www.hp.com/support/tapetools
The compression test will create a file on your tape designed to have a compression ratio of about 2:1, if you get less than 2:1, your compression could be switched off.