If possible, I would be interested in obtaining a copy of the pdf document you 
refer to.  Thanks!

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Stef Coene
Sent: Wednesday, June 30, 2004 12:52 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: raw partitions


On Tuesday 29 June 2004 20:33, asr AT UFL DOT EDU wrote:
> ==> In article <200406291330.i5TDUEmp001568 AT igate.highmark DOT com>, Joni 
> Moyer
<joni.moyer AT HIGHMARK DOT COM> writes:
> > Hello all!
> >
> > I was reading the performance tuning guide and it states that we 
> > should use raw partitions for server db, log and disk storage pool 
> > volumes for an AIX server and I was just wondering if this is true 
> > and what the benefits are of configuring volumes in this manner?
>
> Simpler, faster, less space overhead.
Euh, yes and no.  For AIX and jfs2 file systems, you can enable CIO 
(in /etc/filesystems: "options = rw,cio").  If you do so, your file systems 
are as fast as raw devices.  So you have the benefits of a file system and 
the speed of a raw device.  The I/O requests are directly done on the disk, 
all cache is skipped.
I have a pdf file about this setup for oracle and the speed you can get.  We 
once enabled this on a very busy AIX server and the oracle database was very, 
very fast.

> > As I understand it, if we configure raw logical volumes, the AIX 
> > volume group will need to be applied to a raw logical volume, as 
> > opposed to a standard UNIX filesytem.
For each disk and logical volume, there is a /dev/r* device that you can use.  
This is the raw device version of the normal /dev/* device.

Stef

-- 
stef.coene AT docum DOT org
 "Using Linux as bandwidth manager"
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