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Re: H800 + md1200 Performance problem

From: Glyn Astill <glynastill(at)yahoo(dot)co(dot)uk>
To: Tomas Vondra <tv(at)fuzzy(dot)cz>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: H800 + md1200 Performance problem
Date: 2012-04-05 13:10:01
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
> From: Tomas Vondra <tv(at)fuzzy(dot)cz>

> But the fluctuation, that surely is strange. What are the page cache
> dirty limits, i.e.
> cat /proc/sys/vm/dirty_background_ratio
> cat /proc/sys/vm/dirty_ratio
> That's probably #1 source I've seen responsible for such issues (on
> machines with a lot of RAM).

+1 on that.

We're running similar 32 core dell servers with H700s and 128Gb RAM.

With those at the defaults (I don't recall if it's 5 and 10 respectively) you're looking at 3.2Gb of dirty pages before pdflush flushes them and 6.4Gb before the process is forced to flush its self.

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