tape/backup systems

[Terence Kelleher]

How do large systems typically deal with the problem of backups?  I am
trying to find answers for a 50-100 Gbyte disk system.  

Although 8mm and 4mm have the capacity to handle the amount of data
efficiently, the transfer rates are quite slow, given the volume of
data to move.  Also, the reliability of the heilical scan devices is
well established.

9-track tapes have the speed to handle the volume, but the number of
tapes required and the need to change tapes so often make storage and
operator involvement big issues.

What other solutions exist for Unix systems?
-- 
Terence Kelleher
Encore Computer Corporation
terryk at encore.com