Apologies for the delayed reply, I've just got back from holiday...

For our backups, we use a full + incrementals and rotate the tape 
sets nominally every 3 months. 4 tape sets are used, so we can go 
back at least a year.

nominally?

Yes, the full backups are not scheduled, but manually started. The 
incrementals are automatic. The retention time is 'infinity'. This 
means that we do not *have* to change tape sets at exactly 3 month 
intervals. The tapes do not automatically expire, we have complete 
manual control. It's a little unsophisticated and wouldn't suit a lot 
of people, but it's versatile and for us it works well.

best
-- 
---

REMEMBER - the safety of your data is your responsibility
If it's important to you - ** MAKE A COPY ** or 2 or 3 or 4 or ........

There is only one certainty about storage systems - they *will* fail !

Chris Freemantle
Data Manager
Wellcome Department of Imaging Neuroscience

Tel. +44 (0)20 7833 7472 reception
Tel. +44 (0)20 7833 7496 direct
Fax  +44 (0)20 7813 1420

Home Page:  http://www.fil.ion.ucl.ac.uk