Windows

Lets say you have a 80/160

160 is what is "thought" to be your best compression ratio of 2:1, 80 is if you cannot/do not compress.

Things like jpg's,zip's,compressed databases and video images have really no compression to them and thus you'll only be able to backup 80 GB per tape of this type of file.

Text files, office files, scripts, cleartext logs and the like get fantastic compression and you'll be able to easily get 160 GB of this (and probably lots more) on one tape.

But on most servers you have a combination of cleartext and already compressed files, and a lot in between that get partial compression benefits (such as uncompressed databases etc.). Normally with an 80/160 tape drive you'll get about 100 - 120 GB backed up on an average server (hosting all kinds of files) before it runs out of space.

Zaf