Received: from localhost (maia-4.hub.org [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 93B019FBCC0 for ; Thu, 22 Mar 2007 14:10:59 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-new, port 10024) with ESMTP id 44091-02 for ; Thu, 22 Mar 2007 14:10:37 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from vms040pub.verizon.net (vms040pub.verizon.net [206.46.252.40]) by postgresql.org (Postfix) with ESMTP id 5EC959FBD19 for ; Thu, 22 Mar 2007 14:10:37 -0300 (ADT) Received: from osgiliath.mathom.us ([72.66.31.15]) by vms040.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0JFB00768ED1DLY0@vms040.mailsrvcs.net> for pgsql-performance@postgresql.org; Thu, 22 Mar 2007 12:10:13 -0500 (CDT) Received: from localhost (localhost [127.0.0.1]) by osgiliath.mathom.us (Postfix) with ESMTP id 071116FE0C for ; Thu, 22 Mar 2007 13:10:10 -0400 (EDT) Received: from osgiliath.mathom.us ([127.0.0.1]) by localhost (osgiliath.home.mathom.us [127.0.0.1]) (amavisd-new, port 10024) with LMTP id SFD3uGC5dvCC for ; Thu, 22 Mar 2007 13:10:08 -0400 (EDT) Received: by osgiliath.mathom.us (Postfix, from userid 1000) id AE52D707E0; Thu, 22 Mar 2007 13:10:08 -0400 (EDT) Date: Thu, 22 Mar 2007 13:10:08 -0400 From: Michael Stone Subject: Re: Parallel Vacuum In-reply-to: <200703221655.03068.dimitrik.fr@gmail.com> To: pgsql-performance@postgresql.org Mail-followup-to: pgsql-performance@postgresql.org Message-id: <20070322171007.GH11402@mathom.us> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii; format=flowed Content-disposition: inline X-Virus-Scanned: Debian amavisd-new at mathom.us X-Pgp-Fingerprint: 53 FF 38 00 E7 DD 0A 9C 84 52 84 C5 EE DF 7C 88 References: <200703221435.54408.dimitrik.fr@gmail.com> <200703221605.38460.dimitrik.fr@gmail.com> <20070322151243.GH4102@alvh.no-ip.org> <200703221655.03068.dimitrik.fr@gmail.com> User-Agent: Mutt/1.5.13 (2006-08-11) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200703/341 X-Sequence-Number: 23746 On Thu, Mar 22, 2007 at 04:55:02PM +0100, Dimitri wrote: >In my case I have several CPU on the server and quite powerful storage box >which is not really busy with a single vacuum. So, my idea is quite simple - >speed-up vacuum with parallel execution (just an algorithm): Vacuum is I/O intensive, not CPU intensive. Running more of them will probably make things slower rather than faster, unless each thing you're vacuuming has its own (separate) disks. The fact that your CPU isn't pegged while vacuuming suggests that your disk is already your bottleneck--and doing multiple sequential scans on the same disk will definitely be slower than doing one. Mike Stone