ADSM-L

Re: [ADSM-L] Improving TSM performance - memory related setting

2008-04-07 09:52:08
Subject: Re: [ADSM-L] Improving TSM performance - memory related setting
From: Matthew Glanville <matthew.glanville AT KODAK DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Mon, 7 Apr 2008 09:43:48 -0400
Just a warning, don't necessarily go to 1/2 or 1/8th of your total
physical memory..

If your server has 64 GB of memory, 8 GB (1/8th) for BUFPOOLSIZE is
probably too high.  I would keep it below 1 GB unless you prove to
yourself with some testing that it is helping speed up the backups or
restores.  Just don't look at database cache hit rate.

I think there's some inefficiency in how TSM database cache works, as it
may have to search through that cached memory to find a hit.  When you are
caching 8 GB, that takes some time to search through all that.

You'll see this as the dsmserv processes CPU use will increase the larger
the BUFPOOLSIZE is.  If it takes longer to search through that memory than
it does to read the page from disk, you are hurting performance not
helping it by caching in memory.

Maybe DB2 TSM in version 6 will help this issue.
I tried to put a problem in for it a few years back, but couldn't get
beyond level 2 since no one understood what I was talking about, they kept
thinking the server was slow due to the operating system using it's own
page file to make up for the large memory setting, even though the 64 bit
server had 32 GB of physical memory...  Ahh well.  I can use that other 30
GB for something else.

or is it fixed now?
Matt G.


"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 04/04/2008
03:40:56 AM:

> Bufpoolsize should be set between 1/2 and 1/8 of the among of the
> total physical memory, if I remember well, that is, what best
> practices recommend.
> Also if you modify this parameter you will have to take a look at
> the percentage hit cache (q db f=d) that can be increase (modifying
> the bufpolsize), or perhaps decrease if the setting is incorrect.
> Percentage hit cache must be above 99 %.
>
> I will also recommend to take a look at the performance tuning
> guide, that will let you know more about many settings that can
> increase the performance of your TSM server.
>
> Regards,
> Bernaldo.
>
>
>
> ----- Mensaje original ----
> De: Paul Dudley <pdudley AT ANL.COM DOT AU>
> Para: ADSM-L AT VM.MARIST DOT EDU
> Enviado: viernes, 4 de abril, 2008 5:44:02
> Asunto: Re: [ADSM-L] Improving TSM performance - memory related setting
>
> Currently the BUFPOOLSIZE is set to:
>
> BufPoolSize: 122,880 K
>
> The server has 3 Gb of memory. Is this something I can increase?
>
> Regards
> Paul Dudley
>
> Senior IT Systems Administrator
> ANL IT Operations Dept.
> ANL Container Line
> pdudley AT anl.com DOT au
> 03-9257-0603
> http://www.anl.com.au
>
>
>
> > -----Original Message-----
> > From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On
> > Behalf Of Skylar Thompson
> > Sent: Friday, 4 April 2008 1:05 PM
> > To: ADSM-L AT VM.MARIST DOT EDU
> > Subject: Re: [ADSM-L] Improving TSM performance - memory related
> setting
> >
> > Paul Dudley wrote:
> > > If I recall correctly there is a TSM system setting that relates to
> the
> > > memory available on the server, and you can check and adjust this
> > > setting to improve performance of your TSM server.
> > >
> > >
> > >
> > > Can anyone remind me which setting it is?
> > >
> > >
> >
> > Are you thinking of BUFPOOLSIZE and LOGPOOLSIZE? The former controls
> > the
> > size of the database buffer pool (bounded only by the physical memory
> of
> > the machine), and the latter the size of the temporary transaction
> space
> > in the recovery log (up to 8192 pages IIRC).
> >
> > --
> > -- Skylar Thompson (skylar2 AT u.washington DOT edu)
> > -- Genome Sciences Department, System Administrator
> > -- Foege Building S048, (206)-685-7354
> > -- University of Washington School of Medicine