Re: CBO influences

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 14 Sep 2005 15:01:02 +0000 (UTC)
Message-ID: <dg9dve$5em$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com>

"Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message news:43282C72.36FC_at_yahoo.com...
>
> In terms of mreadtim < sreadtim, we've encountered this on all databases
> at our current site that SAN attached as opposed to JBOD. Haven't
> really got the access to determine whether the SAN is *truly* yielding
> better multiread IO times than singleread IO, but ultimately we've
> resorted to
>
> - collecting system stats
> - tweaking mread to just above sread to enable mbrc inclusion for the cbo
>

That is an interesting tell-tale about what SANs are probably good at, and bad at, doesn't it.

Don't share a SAN if you want to run a high performance OLTP system - they're not very good for small, highly randomised I/Os.

-- 
Regards

Jonathan Lewis

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Received on Wed Sep 14 2005 - 10:01:02 CDT