Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id CFD06B5DBD8 for ; Mon, 12 Sep 2011 20:20:09 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 33984-02 for ; Mon, 12 Sep 2011 23:20:03 +0000 (UTC) X-Greylist: delayed 00:08:43.057121 by SQLgrey-1.7.6 Received: from morework.geizhals.at (morework.geizhals.at [78.142.138.3]) by mail.postgresql.org (Postfix) with ESMTP id BBF32B5DBC5 for ; Mon, 12 Sep 2011 20:20:02 -0300 (ADT) Received: from localhost (morework [127.0.0.1]) by morework.geizhals.at (Postfix) with ESMTP id 78AD01248288 for ; Tue, 13 Sep 2011 01:11:18 +0200 (CEST) X-Virus-Scanned: amavisd-new at geizhals.at Received: from morework.geizhals.at ([127.0.0.1]) by localhost (morework.geizhals.at [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OJtLM2XrEKuJ for ; Tue, 13 Sep 2011 01:11:14 +0200 (CEST) Received: from [192.168.1.28] (mjyrouter [213.235.209.145]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: mjy) by morework.geizhals.at (Postfix) with ESMTPSA for ; Tue, 13 Sep 2011 01:11:14 +0200 (CEST) Message-ID: <4E6E9190.4050005@geizhals.at> Date: Tue, 13 Sep 2011 01:11:12 +0200 From: Marinos Yannikos User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0) Gecko/20110817 Thunderbird/7.0 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Sudden drop in DBb performance References: <4E61D6B4.9090804@ai.wu.ac.at> In-Reply-To: <4E61D6B4.9090804@ai.wu.ac.at> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-2.404 tagged_above=-10 required=5 tests=BAYES_00=-1.9, RP_MATCHES_RCVD=-0.504 X-Spam-Level: X-Archive-Number: 201109/169 X-Sequence-Number: 44945 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