First - I saw your signature - is that Pima County AZ?
You ask some very good questions. I think some of your problem may be some
confusion over ADSM terms - let me see if I can help.
If I understand you, you will back up to regular disk as your primary, pool,
then migrate this pool to Optical for the second level (instead of tape).
You then want to use the remaining disks in the library as a second pool to
handle the backup copypool. ADSM doesn't refer to this as an incremental,
but rather just a backup. Incrementals are what clients do.
As a rule of thumb in the tape world, it is always better to do a backup of a
DASD pool than to try to backup the data after it has been migrated to the
tape pool - requires more drives and more mounts. I would assume that the
same is true in the optical world - you would require two drives to get the
data into the backup copypool.
Planning for your disaster situation always helps out - you have a major
option to consider. If you collocate the copypool, you can reduce the number
of mounts you will need, but with the platter capacity so high, you might
have problems trying to fill the platters before moving them offsite. You
could elect to skip collocation, and fill the platters to capacity, but then
the data for clients would be scattered across many volumes. Also to
consider is how long do you want to leave a copypool volume on site before
you remove it to your offsite storage.
Remember too how ADSM does a restore - it will organize its processing so
that it can make just one pass of the data. In the tape world, if I require
10 tapes, I will only have to mount each tape once - not go back and forth
between them for a single client. So the question is, do you have lots of
different clients to restore in a short time? If so collocation might be
your choice. If you have a relative few clients, or a more reasonable
window, then collocation might be less of an issue.
And don't forget that you can do reclamation processing against your copypool
volumes to consolidate. This doesn't require mounting the volume to be
reclaimed - ADSM assumes the volume is not physically present and copys the
data from the primary pool again.
This has been a long answer - but I hope it helps
Jerry Lawson
jlawson AT thehartford DOT com
______________________________ Forward Header __________________________________
Subject: Copy storage pool question
Author: INTERNET.OWNERAD at SNADGATE
Date: 3/2/98 2:03 PM
I apologize for the length of this message in advance, and warn that
it is very much a beginner's question.
I am having a bit of a conceptual problem with the idea of copy storage
pools: I have an IBM 3995 optical jukebox with a capacity of about
52GB on 20 optical disks. I plan to run incremental backups of clients
nightly to the disk pool and then migrate to optical during the day.
I would like to set up 40GB (or about 15 optical disks) to be allocated
to a primary storage pool and I would like to back up this primary pool
to a copy pool for offsite storage using the remaining five slots in
the optical jukebox.
Here's my question: Should I just perform a nightly incremental backup
of the primary disk pool to the copy pool before migrating the data off
to the optical disks? If I do this, what will I have to do six months
or a year from now in the case of disaster recovery when I have many
more than 20 disks offsite and I need to restore the primary storage
pool? I imagine that reclamation takes care of this somehow, but right
now I can't quite picture what my offsite rotation schedule will have to
be, or how ADSM makes sure that I have a copy of all of my files
offsite.
If anyone out there could share their method for the backup of their
storage pools, I would be very grateful.
Sincerely,
Neal Lauver
Pima County Attorney's Office
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