From: Marinos Yannikos <mjy@geizhals.at>
To: pgsql-performance@postgresql.org
Subject: Re: Sudden drop in DBb performance
Date: Tue, 13 Sep 2011 01:11:12 +0200
Message-ID: <4E6E9190.4050005@geizhals.at> (raw)
In-Reply-To: <4E61D6B4.9090804@ai.wu.ac.at>
References: <4E61D6B4.9090804@ai.wu.ac.at>
Hi,
On 03.09.2011 09:26, Gerhard Wohlgenannt wrote:
> Activating log_min_duration shows for instance this query --- there are
> now constantly queries which take absurdely long.
2 things you should check:
- if your /var/lib/postgresql is on an ext3 fs, I've seen such things
before due to the changes around Linux 2.6.2X that caused long stalls
during fsync() (see https://lwn.net/Articles/328363/ etc.). But if all
your queries take longer than they should and not only a few, that
probably isn't the reason.
- regarding your hardware RAID-5, I've seen some controllers switch the
write cache off quietly for various reasons (battery too old, issues
with disks). Check if it is still enabled, without write caching
enabled, most RAID-controllers will just suck.
Regards,
Marinos
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Subject: Re: Sudden drop in DBb performance
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