ADSM-L

Re: [ADSM-L] Copy stgpool best practises

2014-02-27 12:50:39
Subject: Re: [ADSM-L] Copy stgpool best practises
From: George Huebschman <george.huebschman AT PNC DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 27 Feb 2014 12:48:12 -0500
I give you Wanda's favorite answer, "It depends."

Concepts:
* Primary storage is the repository where you keep data for normal
backup/archive and restore/retrieve.
You can have a disk only primary storage.  You CAN have all disk storage.
There are lots of discussions on ADSM-L about it

* Some environments use disk storage for the initial landing point for
backup/archive data.  That is a Primary Pool.
>From there they migrate data to another pool in the hierarchy, perhaps
tape or virtual tape.
When the data "migrates" it moves off of the first primary storage pool
onto the NEXT primary storage pool.  It is still Primary storage, just on
different media.  That is not a Copy Pool.

* If all you have are Primary pools, you have backed up data, but it isn't
safe.

* Copy pools are a backup (second) copy of the data that reside in Primary
pools.  The "backup stgpool" command makes a thorough copy of the Primary
StgPool.
Often copy pool data on removable tape is taken out of the library daily
and sent offsite for disaster recovery.

You can mix media and it's purpose in many combinations to suit your
situation.
You can go straight to tape...NDMP used to only work that way.
You can use:
Pri-Disk backedup to Copy-Tape  (sounds like your plan A)
Pri-Disk migrated to Pri-Tape backedup to Copy-Tape (sounds like your Plan
B)
Pri-Disk backedup to Copy-Disk and migrate each of them to tape, one to
Pri-Tape and the other to Copy-Tape.
Pri-Disk migrated to Pri-Tape and backedup to Copy-Tape.

TSM will allow you to write to write simultaneously to Primary and Copy
storage pools (but you still need to run storage pool backup.)
(
http://pic.dhe.ibm.com/infocenter/tsminfo/v6r2/index.jsp?topic=%2Fcom.ibm.itsm.srv.doc%2Ft_simulwrite.html
).


Two tape drives is a tight squeeze.  It is the bare minimum for doing tape
reclamation.
     You have to have time for daily client data migration to primary
tape,  client data backup to copy tape, TSM db backups, any db snapshots,
restore activity, and tape reclamation.

So, "it depends":
     You asked if it is a good idea to have  a Primary tape and Copy Tape
storage pool.
Is your system part of a larger business continuity/disaster recovery
plan, or is TSM it?
How much data do you backup every day?
        9TB of data feeding into a TS3100 seems a little mismatched.  I
work with TS3310 and TS3500 (3584) libraries.  I don't have any experience
with the TS3100.  Glancing at it on google it looks very small.
     If you do a backup stgpool for your primary disk pool, you need as
much space as is in the primary pool.
     If you also have a primary tape pool (primary disk migrated to
primary tape, copied (backed up) to copy tape) you need just as much more
storage.  If you are removing the copy pool media regularly (daily,
weekly) then you don't need too much more library space than your primary
pool requires, but you need some more...which depends on how much your
data changes and how often you eject copy media and how many scratch you
keep in the library.
How long do you retain your data?
How long does data stay in the disk level of the hierarchy before it
migrates?
Do you do a lot of restore/recover or is that an infrequent task?
What throughput do you have on your tape drives?  Could you get another
tape drive or two perhaps?
Would it be efficient enough to use less disk and more tape?
     If you don't restore a lot, and or don't restore a lot of really
large objects (db files, entire filesystems and such) then maybe less disk
would be more cost effective.
     You can't compensate for insufficient tape drive capacity by adding
more disk  (been there!).

So the answer is, yes, that's a good plan, having tape primary and copy
pools behind a disk primary storage pool, but you need to consider your
tape capacity. and whether you need all that disk.
   Anyone else please chime in.  I am still wrapping my mind around
thinking past being an admin.  I am sure I have overlooked things I might
have added.


You can go here to look up old threads:
http://adsm.org/lists/html/ADSM-L/

George Huebschman (George H.)
(301) 699-4013
(301) 875-1227 (Cell)



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