ADSM-L

Re: Setting up a tape rotation

1998-09-03 17:09:34
Subject: Re: Setting up a tape rotation
From: Peter Gathercole <peter.gathercole AT VIRGIN DOT NET>
Date: Thu, 3 Sep 1998 22:09:34 +0100
What we do is to use the Disaster Recovery Manager to keep track of two copy
pools, which are updated on alternate days. By using this mechanism, we have
the additional security of more than media volume containing any particular
piece of information. We will have at least three media volumes with a
particular file on it. One in the library, and two in our offsite vault.

This is a requirement for the in-house DR schemes at my current employment.

Of course, you have to keep at least two days of database backup, and make sure
that the reuse delay on the copygroups is sufficient that tapes are not
re-cycled before the database copies are recovered.

The problem with using just a single storage pool, and allowing the continued
incramental policy to allow point-in-time recovery is that if a file is written
and never changed, then it is only resident on a single tape volume. If this
volume were to go bad, then the data would be lost. The same would be true if
you had multiple incramental copies an colocation turned on. All of your data
for a single node would be resident on a single (or few) volumes. This makes
you very vulnerable to media failure. We have two offsite copies so that if a
tape in our primary pool goes bad, one of the offsite copies can be recalled
from the vault, and we still have another copy offsite. This also allows for
tapes in the vault to go bad (the last thing you need in a DR situation is to
find that your only vault copy is on media that has become unusable).

Peter Gathercole
Open Systems Consultant.

Dan Giles wrote:

> Boy, I wish I had a dollar (U.S., of course) for everyone who's ask this
> question of me.
>
> First, take your traditional concept of tape rotation and throw it out the
> window. ADSM works on a continuous incremental scheeme, and you should let
> it work this way. You will save both time and $$$ on tapes. If, for some
> reason, you do need monthly snapshots (for legal reasons, say), then use
> the archive function. Let ADSM handle its own tape rotation using its own
> reclamation procedures.
>
> What I am working on here is to get people to think of their RESTORE and DR
> requirements. For instance, "I need to restore this directory tree to a
> point in time anywherer up to 30 days ago". In this case, I will tell ADSM
> to keep an unlimited number of file from this directory tree for up to 30
> days.
>
> This probably hasn't helped too much, but hopefully will get you thinking
> from another perspective.
>
> From: Roberto Mannella <rmannell AT MANITOULINTRANSPORT DOT COM> on 09/01/98 
> 11:10
>       AM GMT
>
> Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
>
> To:   ADSM-L AT VM.MARIST DOT EDU
> cc:    (bcc: ADSM)
> Subject:  Setting up a tape rotation
>
> Hello folks:
>
> I'm relatively new to the ADSM world so please bear with what may be a
> seemingly stupid question.
>
> I will be running ADSM for OS/400 using a Magstar 3570 tape unit to back up
> my Lotus Notes server running on an IPCS.  I would like to set up a daily
> tape rotation of DAY1-4, WEEK1-3, and MONTHA-C.
>
> >From the documentation I have and some Redbooks I've been reading, I can't
> seem to figure out how ADSM implements a tape rotation - best I can figure
> is a manual tape library but then a single tape is used until it's full,
> then it requests the next tape, etc.
>
> IBM says it can't be done without making volumes available and unavailable.
> This would require writing code and is not desirable to have something like
> that to maintain.
>
> Any suggestions would be greatly appreciated.
>
> Thanks.
>
> --
> 8~)
> Roberto
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