Re: disk and db volume sizes

For storage pools, TSM will create a thread (concurrent I/O ) for each of
the storage pool volumes, if you have that many sessions going.

So again, if you have a lot of physical disks for the storage pools, you
spread the storage pool volumes across those disks.

However, in this case it's all problematic - if you are talking 1 big raid-5
array, and 1 channel, it's all very problematic.  You will get a write
penalty on the RAID-5, and the storage pool I/O will conflict with the log
and DB I/O.  So you need to think about how many TOTAL I/O operations you've
got going on, and keep it down to a smaller number, maybe the number of
physical disks in the RAID group, dunno.

If you are connected to a Shark (IBM ESS) or EMC disk with GB of cache
memory in front of the disk, you can pump a cazillion IO's/sec into those
things - more than your Windows server can send, so it won't matter much.

Anything less, I'd say if you are worried about performance, you should
split off some of the physical disks into raid-1 for the DB.  But, with only
1 channel, it's unclear whether that will help.

You can find many, many permutations of this disscussion in
search.adsm.org.....





-----Original Message-----
From: French, Michael [mailto:Michael.French AT SAVVIS DOT NET]
Sent: Thursday, January 15, 2004 2:28 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: disk and db volume sizes


        I talked to a guy at IBM several months back and his suggestions
were that you should analyze the number of concurrent sessions that you
have going at anyone one time and create an equal number of DB volumes.
I usual have about 20 concurrent backup sessions going during my various
backup windows so I am in the process of breaking my DB volumes into
smaller ones.  He told me that this was a thread issue with how TSM
talks to the DB volumes (hope I got that part right).  As for the log
volumes, I was told this is like a paging file, make one large one.

        If anyone at there has counter views, speak up now before I
start tearing apart my systems!

Michael French
Savvis Communications
IDS01 Santa Clara, CA
(408)450-7812 -- desk
(408)239-9913 -- mobile



-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Joe Crnjanski
Sent: Thursday, January 15, 2004 10:04 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: disk and db volume sizes


Hi Everyone,

Does anybody know what is the optimum (best performance and reliability)
size for disk pool and database volumes.

Is it better to have one big volume (500GB example) or 5x100GB. Here we
are talking around 1TB of RAID5 size on Win2k server. All volumes would
reside on the same RAID 5 array and on 1 channel on IBM 4MX 160 RAID
controller. Same question for db volumes; size of volume vs. number of
volumes.

Thanks,

Joe Crnjanski
Infinity Network Solutions Inc.
Phone: 416-235-0931 x26
Fax:     416-235-0265
Web:  www.infinitynetwork.com