Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id 65A672E0030 for ; Tue, 17 Jun 2008 13:32:19 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 04981-06 for ; Tue, 17 Jun 2008 13:32:12 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from westnet.com (westnet.com [216.187.52.2]) by developer.postgresql.org (Postfix) with ESMTP id 5E8572E0042 for ; Tue, 17 Jun 2008 13:32:13 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m5HGWBMG015005; Tue, 17 Jun 2008 12:32:11 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m5HGWA1r015000; Tue, 17 Jun 2008 12:32:10 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Tue, 17 Jun 2008 12:32:10 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Andrew Sullivan cc: pgsql-performance@postgresql.org Subject: Re: Which hardware ? In-Reply-To: <20080617154215.GI68434@commandprompt.com> Message-ID: References: <20080617142501.GG68434@commandprompt.com> <20080617154215.GI68434@commandprompt.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200806/83 X-Sequence-Number: 30433 On Tue, 17 Jun 2008, Andrew Sullivan wrote: > A running JVM is necessarily going to use some memory, and that is > memory use that you won't be able to factor out properly when developing > models of your database system performance. Now you've wandered into pure FUD. Tuning maximum memory usage on a Java app so you can model it is straightforward (albeit a little confusing at first), and in most cases you can just sample it periodically to get a good enough estimate for database tuning purposes. JVMs let you adjust maximum memory use with -Xmx , and if anything the bigger problem I run into is that using too much memory hits that limit and crashes Java long before it becomes a hazard to the database. This is a system with 8GB of RAM here; having some Tomcat instances co-existing with the database when there's that much room to work is not that hard. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD