ADSM-L

Re: [ADSM-L] guide for sizing storage pools

2010-08-04 20:33:33
Subject: Re: [ADSM-L] guide for sizing storage pools
From: Robert Clark <robert.clark7 AT USBANK DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 4 Aug 2010 17:32:44 -0700
Back when only one migration process was allowed per pool, having multiple
pools allowed for some parallelism.

Ideally the disk storage pools should come out of two different volume
groups.  That way you can give back all the LUNS that comprise volume
group A, while the storage admins do whatever they need to do, and then
later on do the same thing with the LUNS for volume group B.

I really don't like one big disk storage pool. You can't say much
intelligible about how one pool gets used. It is either big enough, or it
is not. With several pools, you can monitor percent full/utilized over
several days to decide which ones need resizing. (Moving volumes from pool
to pool is easy.) Its like a brix cup; if all pools fill at a similar
rate, then they are correctly sized. (Oversimplified, I know.)

I'm not a big fan of one HUGE disk storage pool either. (A weeks worth for
example.) People tend to accept a huge slow pool in liu of a smaller
faster pool, and I'd rather have 2-3 days worth of fast disk storage pool
than a week's worth of slow pool. (Unless you've neglected your tape
environment for years, the difference in restore speed between disk and
tape for days 3- 7 shouldn't matter that much.) Also, you don't save any
work for the system. Very little will age out of the disk storage pool
before needing to be migrated to tape. (Even if you do have a week's
worth.) Have you ever moved a waterbed? Big pools are about that much
hastle.

[RC]



From:
David McClelland <tsm AT NETWORKC.CO DOT UK>
To:
ADSM-L AT VM.MARIST DOT EDU
Date:
08/04/2010 03:11 PM
Subject:
Re: [ADSM-L] guide for sizing storage pools
Sent by:
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>



I echo Wanda's points here, expanding that 1) another good reason for
having
at least an entire night's backup on DISK storage pool is that many of
your
restore requests may be for data within the last 24-48 hours and may be
most
quickly serviced by restore from DISK rather than TAPE; 2) one 'good
reason'
some have chosen in the past to separate storage pools is if they're
managing different types of backup/archive data, for example, OS/binaries
which are typically pretty small and static, versus SQL Server or Oracle
database backups which are typically very large files kept for a set
number
of days - tape reclamation comes into play here, ensuring you make best
usage of your tape volumes, and having these large data types expire at
around the same time on the same tape typically can reduce your
administrative tape reclamation overhead (cf. wise words along the lines
of
the best reclamation is that you don't have to do).
_______________
David McClelland
London, UK

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Prather, Wanda
Sent: 04 August 2010 22:41
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] guide for sizing storage pools

1) ROT:  If you are planning to back up to disk and migrate to tape, your
disk pool should be large enough to hold at least one complete night's
backup.  (That way if you have tape drive problems in the middle of the
night, your backups will continue to run and you can kick the robot in the
morning.)

2) One, until you have a really good reason to make more.  If you have all
your space in 1 pool, TSM can make the most flexible use of it.  (If you
have it divided into 2 pools, Murphy will insure that one pool will run
out
of space on the day the other is only 10% used.)  An example of needing 2
disk pools:  you are creating 2 tape pools, one which will be copied to go
offsite and the other not copied to go offsite.  If you want to migrate to
2
separate tape pools, you have to start with 2 separate disk pools.

Backing up different types of OS, having different domains with different
retention times, etc. do not require any type of pool separation.  Use 1
as
long as you can, let TSM do the work for you..

W




-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Dana Holland
Sent: Wednesday, August 04, 2010 5:32 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] guide for sizing storage pools

A typical newbie question, I'm sure - but is there a guide to help
determine
how to size storage pools?  And how many storage pools you should create?
I
found a Redbook from 2006, but is there anything more recent?


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