We keep 6 copies of active files for 60 days; 1 copy of deleted files
for 60 days.
Space in the tape library is at a premium, or I wouild keep more copies
but stick to the 60 day limit.
The number of days to keep the extra backup versions has had more impact
on the size of the library than the number of versions, because we found
that most files don't change at all, and only a small number of files
use all 6 versions.

We figured after 60 days it is unlikely that anybody remembers what the
nth version back really was, anyway.
Our experience is that with this scheme, we get about 1 person per
quarter that wants something restored that we don't have.  And in those
cases, they usually can't tell you whether it was 90 days old or 180, so
increasing the time limit would be unlikely to help those people, unless
we went to infinity.

I would suggest reducing your limit from 18 months to 15, and see how
many people have a problem; then you can guage what the impact would be
if you reduced it further and whether the cost is acceptable.


===============================================================
Wanda Prather
Johns Hopkins Applied Physics Lab
301-953-6000 X8769
wanda_prather AT jhuapl DOT edu

"Intelligence has much less practical application than you'd think."
              - Scott Adams/Dilbert
===============================================================




        ----------
        From:   Yelle, Michael
2-3823[SMTP:MGY4V AT hscmail.mcc.virginia DOT edu]
        Sent:   Tuesday, January 13, 1998 10:24 AM
        To:     ADSM-L AT vm.marist DOT edu
        Subject:        Number of backup copies to keep

        Questions: What is a "reasonable and customary"  number of
backup copies
        to keep? How long should they be kept? We are a University
Hospital
        environment.

        Background: We use adsm to backup a number of Novell, Widows/NT
and AIX
        boxes. We currently have 900+ gigabytes of ADSM managed data in
a
        TAPEPOOL.  It is growing at about 100 gigabytes a month.  Our
default
        policy currently is to keep 15 copies (VEREXISTS) of each file
for 18
        months (RETEXTRA). We would like to reduce this value to control
growth
        in the storage pool.

        For some of our data we have specific business requirements to
keep a
        certain number of copies for a certain period of time. My
question is
        not concerned with this data.  Rather it is directed at user
data owned
        by many different people on Novell Fileservers. No specific
retention
        business requirements have been mandated for this data.

        Any help would be appreciated.