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Re: Choosing a filesystem

From: Guillaume Cottenceau <gc(at)mnc(dot)ch>
To: Craig James <craig_james(at)emolecules(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Choosing a filesystem
Date: 2008-09-12 08:38:45
Message-ID: 873ak5iwru.fsf@mnc.ch (view raw or flat)
Thread:
Lists: pgsql-performance
Craig James <craig_james 'at' emolecules.com> writes:

> The performance improvement of a BB cache is amazing.

Could some of you share the insight on why this is the case? I
cannot find much information on it on wikipedia, for example.
Even http://linuxfinances.info/info/diskusage.html doesn't
explain *why*.

Out of the blue, is it just because when postgresql fsync's after
a write, on a normal system the write has to really happen on
disk and waiting for it to be complete, whereas with BBU cache
the fsync is almost immediate because the write cache actually
replaces the "really on disk" write?

-- 
Guillaume Cottenceau, MNC Mobile News Channel SA, an Alcatel-Lucent Company
Av. de la Gare 10, 1003 Lausanne, Switzerland - direct +41 21 317 50 36

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