X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id AEE62D7331 for ; Sun, 20 Nov 2005 08:55:17 -0400 (AST) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 76131-05 for ; Sun, 20 Nov 2005 12:55:18 +0000 (GMT) X-Greylist: from auto-whitelisted by SQLgrey- Received: from floppy.pyrenet.fr (floppy.pyrenet.fr [194.116.145.2]) by svr1.postgresql.org (Postfix) with ESMTP id B8EFFD6810 for ; Sun, 20 Nov 2005 08:55:13 -0400 (AST) Received: by floppy.pyrenet.fr (Postfix, from userid 106) id D248C31059; Sun, 20 Nov 2005 13:55:16 +0100 (MET) From: William Yu X-Newsgroups: pgsql.performance Subject: Re: Hardware/OS recommendations for large databases ( Date: Sun, 20 Nov 2005 04:55:14 -0800 Organization: Hub.Org Networking Services Lines: 24 Message-ID: References: <437FE2E4.5040600@rentec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@news.hub.org User-Agent: Mozilla Thunderbird 1.0 (X11/20041206) X-Accept-Language: en-us, en In-Reply-To: <437FE2E4.5040600@rentec.com> To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0 required=5 tests=[AWL=0.000] X-Spam-Score: 0 X-Spam-Level: X-Archive-Number: 200511/408 X-Sequence-Number: 15665 Alan Stange wrote: > Luke Lonergan wrote: >> The "aka iowait" is the problem here - iowait is not idle (otherwise it >> would be in the "idle" column). >> >> Iowait is time spent waiting on blocking io calls. As another poster >> pointed out, you have a two CPU system, and during your scan, as > > iowait time is idle time. Period. This point has been debated > endlessly for Solaris and other OS's as well. I'm sure the the theory is nice but here's my experience with iowait just a minute ago. I run Linux/XFce as my desktop -- decided I wanted to lookup some stuff in Wikipedia under Mozilla and my computer system became completely unusable for nearly a minute while who knows what Mozilla was doing. (Probably loading all the language packs.) I could not even switch to IRC (already loaded) to chat with other people while Mozilla was chewing up all my disk I/O. So I went to another computer, connected to mine remotely (slow...) and checked top. 90% in the "wa" column which I assume is the iowait column. It may be idle in theory but it's not a very useful idle -- wasn't able to switch to any programs already running, couldn't click on the XFce launchbar to run any new programs.