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Re: O_DIRECT setting

From: Guy Thornley <guy(at)esphion(dot)com>
To: Mark Wong <markw(at)osdl(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: O_DIRECT setting
Date: 2004-09-30 07:02:32
Message-ID: 20040930070232.GA8139@conker.esphion.com (view raw or flat)
Thread:
Lists: pgsql-performance
Sorry about the belated reply, its been busy around here.

> > Incidentally, postgres heap files suffer really, really bad fragmentation,
> > which affects sequential scan operations (VACUUM, ANALYZE, REINDEX ...)
> > quite drastically. We have in-house patches that somewhat alleiviate this,
> > but they are not release quality. Has anybody else suffered this?
> > 
> 
> Any chance I could give those patches a try?  I'm interested in seeing
> how they may affect our DBT-3 workload, which execute DSS type queries.

Like I said, the patches are not release quality... if you run them on a
metadata journalling filesystem, without an 'ordered write' mode, its
possible to end up with corrupt heaps after a crash because of garbage data
in the extended files.

If/when we move to postgres 8 I'll try to ensure the patches get re-done
with releasable quality

Guy Thornley

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Subject: Re: O_DIRECT setting

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