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RE: Defrag tool on the Oracle database server

From: Adrian Turner <adrian_at_astenconsultants.co.uk>
Date: Mon, 9 Feb 2004 07:42:25 -0000
Message-ID: <AKEIKEDFKHJIDIKFJFGDGEHKCAAA.adrian@astenconsultants.co.uk>


I can give you a reason for using disk fragmenting datafiles that I've encountered in the real world.

We moved a 150GB data warehouse to a Win2K server running on an EVA SAN. The target server had 8 CPUs available so we unzipped the files concurrently 8 ways parallel to increase deployment speed.

When testing it was discovered performance was 20% slower on better disk hardware. Indeed the chosen example job was still full table scanning, but the 10046 showed the scattered read I/O rate was often much slower than the minimum. Pfiles etc were left the same as per the source server.

After a lot of investigating of the new SAN, the SA reported the oracle datafiles were heavily fragmented. Because of running the multiple unzips the files had been fragmented into thousands of 512Kish chunks. An example 2K datafile had 4000+ fragments! So we defragged on the OS (with a shutdown db) and performance increased to better than the source system speed.

HTH Adrian

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Paul Drake Sent: 09 February 2004 03:00
To: oracle-l_at_freelists.org
Subject: Re: Defrag tool on the Oracle database server

Jared,

do you mean in a useful paper form, as opposed to a powerpoint presentation? that presents a slight problem.

the powerpoint presentation of "Nimda ate my Database!" that I was fortunate enough to be able to deliver at RMOUG 2003 is still available, but it was not very useful. It does cover filesystem permissions.

I never did deliver the finished paper, just my notes to those that asked for them. That paper should have been writted and published on the RMOUG site (and the OOUG site).

I'll see what I can dig up for you. Some of the w2k version is obsoleted by w2k3 server, but the principles still apply.

If its for 9.2 / w2k Server I think that I can produce something rather quickly. Sounds like a good SANS paper topic. I'd like to become a *certified* bastard DBA from hell /BOFH in the near future.

It wouldn't be an Oracle User group conference for me if I wasn't having to put together something for it a couple of days before. Plane ride Tuesday, that should provide some excellent writing time.

The past year went by very quickly.

Paul



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Received on Mon Feb 09 2004 - 01:42:25 CST

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