kewl.

Well, 8k request out of PG kernel might turn into an "X"Kb request at
disk/OS level, but duly noted.

Did you scan the code for this, or are you pulling this recollection from
the cognitive archives? :-)



-----Original Message-----
From: Jim C. Nasby [mailto:decibel@decibel.org]
Sent: Tuesday, April 19, 2005 8:12 PM
To: Mohan, Ross
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] How to improve db performance with $7K?


On Mon, Apr 18, 2005 at 06:41:37PM -0000, Mohan, Ross wrote:
> Don't you think "optimal stripe width" would be
> a good question to research the binaries for? I'd
> think that drives the answer, largely. (uh oh, pun alert)
>
> EG, oracle issues IO requests (this may have changed _just_
> recently) in 64KB chunks, regardless of what you ask for.
> So when I did my striping (many moons ago, when the Earth
> was young...) I did it in 128KB widths, and set the oracle
> "multiblock read count" according. For oracle, any stripe size
> under 64KB=stupid, anything much over 128K/258K=wasteful.
>
> I am eager to find out how PG handles all this.

AFAIK PostgreSQL requests data one database page at a time (normally 8k). Of course the OS might do something different.
--
Jim C. Nasby, Database Consultant decibel@decibel.org
Give your computer some brain candy! www.distributed.net Team #1828

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