ADSM-L

Re: What stripe size to use for TSM DB, LOG

2002-10-03 01:40:59
Subject: Re: What stripe size to use for TSM DB, LOG
From: Roger Deschner <rogerd AT UIC DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 3 Oct 2002 00:31:51 -0500
Im my experience, it is better NOT to stripe the TSM database.
Fragmentation is a way of life for the ITSM Database. This insures that
I/O seek locations will be randomly spread across the entire database.
If you stripe, you increase the number of heads that must move for each
I/O operation. This hurts your potential multiprogramming level - better
to have just one head move for each operation, freeing the other heads
for use by other threads. So, don't stripe, unless you have the luxury
of a completely idle system when you do DBBackup. On our system,
everything happens all the time, and the best we can hope for is
"somewhat less of everything else" during a DBBackup.

The Log is VERY different; striping can help. The Log is run as a
sequential, circular buffer.

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu


On Wed, 2 Oct 2002, Seay, Paul wrote:

>Stripe size is very hardware dependent.
>
>Paul D. Seay, Jr.
>Technical Specialist
>Naptheon Inc.
>757-688-8180
>
>
>-----Original Message-----
>From: Kilchenmann Timo [mailto:Timo.Kilchenmann AT BECHTLE DOT CH]
>Sent: Wednesday, October 02, 2002 11:25 AM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: What stripe size to use for TSM DB, LOG
>
>
>Dear all,
>
>>>From a previous threat I learned, that TSM fills a DB volume an than goes to
>the next one. Same is true for the LOG volumes - no "load balancing" like on
>STG Volumes via client sessions.
>
>In this case (DB & LOG) I plan to use AIX LVM to stripe the logical volumes
>over the available physical disks. The question here is what stripe size
>should I use? Any suggestions?
>
>Many thanks in advance!!!
>
>Timo
>

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