Received: from localhost (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id B1DEB6504CA for ; Tue, 9 Dec 2008 13:46:42 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 33750-04 for ; Tue, 9 Dec 2008 13:46:39 -0400 (AST) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from yw-out-2324.google.com (yw-out-2324.google.com [74.125.46.31]) by mail.postgresql.org (Postfix) with ESMTP id 50590650490 for ; Tue, 9 Dec 2008 13:46:39 -0400 (AST) Received: by yw-out-2324.google.com with SMTP id 3so33699ywj.73 for ; Tue, 09 Dec 2008 09:46:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=k/X8bCS/NFedekI3pa6kywTb4qY2MOURcx+Ph8mRXOU=; b=ZEaBzhxvjrfsztCLoWCHtPqzLaKz7EuucJ3Q0SoDhG3h2NFSDwBPpU5aA8YTtJQ5qx h6pHwPIzUMOukQAfUUdm9ldbj0PC3FYGqNCemXJp6A0UzpCmE/1EXgu2ScBpxku/GMDQ YYy+P4h6mHwDeyg/kewJ1bzt4zyGnhQjD5rTo= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=ZGfAhqb8nK0QeCdR0Qf2T8rifk9YPxYtg62gcf9Orad+2jN0V0vzrIQ6hvYdgTReTN MbKVGjYCl2nF9/2osjS/FbgF1fOQOhaso+SeLJp5zNSRa/yfMdCRRCZnsd/WvNzYHfOu qeEjVXD5f943uSwXpL+aOtFibHLNhm2sEsLys= Received: by 10.114.191.1 with SMTP id o1mr251167waf.209.1228844797571; Tue, 09 Dec 2008 09:46:37 -0800 (PST) Received: by 10.114.133.4 with HTTP; Tue, 9 Dec 2008 09:46:37 -0800 (PST) Message-ID: Date: Tue, 9 Dec 2008 10:46:37 -0700 From: "Scott Marlowe" To: "Matthew Wakeling" Subject: Re: Need help with 8.4 Performance Testing Cc: "pgsql-performance@postgresql.org" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200812071138.01215.josh@agliodbs.com> <493E6DBE.2040605@verizon.net> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200812/85 X-Sequence-Number: 32121 On Tue, Dec 9, 2008 at 10:35 AM, Matthew Wakeling wrote: > On Tue, 9 Dec 2008, Scott Marlowe wrote: >> >> I wonder how many hard drives it would take to be CPU bound on random >> access patterns? About 40 to 60? And probably 15k / SAS drives to >> boot. Cause that's what we're looking at in the next few years where >> I work. > > There's a problem with that thinking. That is, in order to exercise many > spindles, you will need to have just as many (if not more) concurrent > requests. And if you have many concurrent requests, then you can spread them > over multiple CPUs. So it's more a case of "How many hard drives PER CPU". > It also becomes a matter of whether Postgres can scale that well. For us, all that is true. We typically have a dozen or more concurrent requests running at once. We'll likely see that increase linearly with our increase in users over the next year or so. We bought the machines with dual quad core opterons knowing the 6,8 and 12 core opterons were due out on the same socket design in the next year or so and we could upgrade those too if needed. PostgreSQL seems to scale well in most tests I've seen to at least 16 cores, and after that it's anyone's guess. The Sparc Niagra seems capable of scaling to 32 threads on 8 cores with pgsql 8.2 quite well. I worry about the linux kernel scaling that well, and we might have to look at open solaris or something like the solaris kernel under ubuntu distro to get better scaling.