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Re: The results of my PostgreSQL/filesystem performance tests

From: "Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au>
To: "Sean Chittenden" <sean(at)chittenden(dot)org>,"Bill Moran" <wmoran(at)potentialtech(dot)com>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: The results of my PostgreSQL/filesystem performance tests
Date: 2003-08-29 01:59:50
Message-ID: 082e01c36dd1$3bf1f150$2800a8c0@mars (view raw or flat)
Thread:
Lists: pgsql-performance
> I'm likely going to make this the default for PostgreSQL on FreeBSD
> starting with 7.4 (just posted something to -hackers about this)f.  If
> you'd like to do this in your testing, just apply the following patch.
>
> Right now PostgreSQL defaults to 8K blocks, but FreeBSD uses 16K
> blocks which means that currently, reading two blocks of data in PG is
> two read calls to the OS, one reads 16K of data off disk and returns
> the 1st page, the 2nd call pulls the 2nd block from the FS cache.  In
> making things 16K, it avoids the need for the 2nd system call which is
> where the performance difference is coming from, afaikt.  -sc

Are you _sure_ this won't cause any atomicity problems?  Can FreeBSD write
16k as an atomic unit?

Chris


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