This is always a difficult concept to get people to understand, especially
if they've only worked in a client/server world. Previous products for
client/server were limited to what they could perform via slow SCSI
connections to equally slow tape devices which were, at best, unreliable.

Yes, you do have one copy of the data residing on the host machine, but
with the use of copypools (very highly recommended), migration pools
(equally important for storage management), and offsite copies (the
ever-popular disaster recovery scenarios), the chances of losing ALL copies
all at the same time would probably be due to total nuclear holocaust ---
and in that instance, who cares anyway?

Make certain your customers understand that any one time, their files
reside in numbers of places so in the event of failure of one media type
(dasd, for instance), the tape copies are available for restore of data.
And in the event that tape media fails, dasd media is available. And if for
some reason everything in your main facility takes a quick and immediate
dive, your offsite copies are available for restores. They are covered far
more reasonably and cost-effectively that they would be with the older
methods of file backup.

Hope this helps.

C.L.Cannam
Storage Management
GENAM/St. Louis, MO/USA
ccannam AT genam DOT com




Hilton Tina <HiltonT AT TCE DOT COM> on 06/11/98 02:06:16 PM

Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

To:   ADSM-L AT VM.MARIST DOT EDU
cc:    (bcc: Cindy Cannam)
Subject:  Re: ADSM Paradigm




Tim,
We only do incremental backups.  The chances of a backup file remaining
for life on the same tape are fairly low.  As backups expire and tape
utilization decreases, the tapes are reclaimed and the files moved to
another tapes.  Also, if you use copy pools (highly recommended) you can
easily restore a local volume that may have become corrupted.  Another
thing that some people do, and I intend to implement sometime soon, is
to have a script that will issue move data commands on tapes that
haven't been referenced in a while.  We've been using ADSM for a couple
of years now, and although we've had some tapes go bad we haven't lost a
backup file yet.
I hope this relieves your concerns.
Tina Hilton
> -----Original Message-----
> From: Tim Rushforth [SMTP:trushfor AT CITYGW.CITY.WINNIPEG.MB DOT CA]
> Sent: Thursday, June 11, 1998 1:14 PM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      ADSM Paradigm
>
> We are about to Trial ADSM and I am struggling with the ADSM Paradigm
> of "incremental backup forevever".
>
> I understand the concepts of ADSM and how this is possible.  One of my
> concens would be relying on only one copy of a file on tape with this
> apporach.
>
> I am interested in how current users of ADSM perform their backups.
>
> Do you do any full backups?
> If so, do you route these backups to different tapes?
> etc.
>
> Thanks for any information.
>
> Tim Rushforth
> City of Winnipeg
> trushfor AT city.winnipeg.mb DOT ca