Re: SAN/NAS options - Mailing list pgsql-performance

From Jim C. Nasby
Subject Re: SAN/NAS options
Date
Msg-id 20051217002525.GC53809@pervasive.com
Whole thread Raw
In response to Re: SAN/NAS options  (Michael Stone <mstone+postgres@mathom.us>)
Responses Re: SAN/NAS options
List pgsql-performance
On Fri, Dec 16, 2005 at 05:51:03PM -0500, Michael Stone wrote:
> On Fri, Dec 16, 2005 at 04:18:01PM -0600, Jim C. Nasby wrote:
> >Even if you're doing a lot of random IO? I would think that random IO
> >would perform better if you use smaller (8K) blocks, since there's less
> >data being read in and then just thrown away that way.
>
> The overhead of reading an 8k block instead of a 32k block is too small
> to measure on modern hardware. The seek is what dominates; leaving the
> read head on a little longer and then transmitting a little more over a
> 200 megabyte channel is statistical fuzz.

True, but now you've got 4x the amount of data in your cache that you
probably don't need.

Looks like time to do some benchmarking...
--
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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