I have a hard time making my potential customers comfortable with this
concept, too.  If you don't mind, I'll try polishing my explanation a little
on you.

Personally, I find it safest to avoid the word "incremental" when I'm talking
to my clients for a couple reasons;  the first of which addresses your
question, "Do you do any full backups?"  ADSM considers a file eligible for
backup if it has changed since the last time the backup procedure was invoked
or if a file is new.  Therefore, the first time you invoke ADSM it does a
"full" backup because every file is new to the ADSM server.  So in that
sense, yes, we do full backups the first time ADSM is used.

The second reason for avoiding the word incremental is because for anyone who
has any "history" with backups the word incremental implies the scenario -
restore the most recent full backup and apply all the daily incrementals to
it to bring it up to date.  That is NOT what happens with ADSM.  The ADSM
database keeps track of all the information necessary to restore each and
every file to it's most current state when the "disaster" occurred.  This is
all taken care of behind the scenes.

For your other question, you do only have the one tape copy of a file, but as
I understand it ADSM is constantly moving files from tape to tape as the data
on a tape expires.  This merge/purge process insures your one copy isn't
sitting on the same (possibly damanged) tape for very long, and if a file is
lost or corrupted, the next incremental backup will put another copy out
there.

We do have customers who simply can't be talked out of the "monthly/yearly
full backup" and full backups can be forced (either by archiving, or
selective backup, or changing the drive label), but it is so completely
unnecessary with ADSM that we try very hard to convince people they don't
need to do this, and when they insist on doing it anyway, we charge them
extra for it.

Hope that wasn't way too much more than you wanted.




ADSM-L AT VM.MARIST DOT EDU on 06/11/98 01:54:28 PM
Please respond to ADSM-L AT VM.MARIST DOT EDU @ INTERNET
To: ADSM-L AT VM.MARIST DOT EDU @ INTERNET
cc:
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