From owner-freebsd-geom@FreeBSD.ORG Mon Nov 9 16:24:42 2009 Return-Path: Delivered-To: freebsd-geom@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7AF56106566C for ; Mon, 9 Nov 2009 16:24:42 +0000 (UTC) (envelope-from 000.fbsd@quip.cz) Received: from elsa.codelab.cz (elsa.codelab.cz [94.124.105.4]) by mx1.freebsd.org (Postfix) with ESMTP id 361638FC15 for ; Mon, 9 Nov 2009 16:24:42 +0000 (UTC) Received: from localhost (localhost.codelab.cz [127.0.0.1]) by elsa.codelab.cz (Postfix) with ESMTP id F112E19E027 for ; Mon, 9 Nov 2009 17:24:40 +0100 (CET) Received: from [192.168.1.2] (r5bb235.net.upc.cz [86.49.61.235]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by elsa.codelab.cz (Postfix) with ESMTPSA id 6081419E023 for ; Mon, 9 Nov 2009 17:24:38 +0100 (CET) Message-ID: <4AF84245.7070108@quip.cz> Date: Mon, 09 Nov 2009 17:24:37 +0100 From: Miroslav Lachman <000.fbsd@quip.cz> User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.9.1.4) Gecko/20091017 SeaMonkey/2.0 MIME-Version: 1.0 To: freebsd-geom@FreeBSD.org Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 7bit Cc: Subject: gjournal and calculation of the size of journal provider X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Nov 2009 16:24:42 -0000 What is the right rule for journal size calculation? There are two sources stating different things. 1] journal size depends on disk write speed http://lists.freebsd.org/pipermail/freebsd-fs/2006-June/002016.html "For example your disk can write at 60MB/s. Journal switch time is 10 seconds. The journal provider has to have place to keep two journals (active and inactive). So bascially you need 60*10*2MB + gjournal headers." 2] journal size depends on RAM size http://www.freebsd.org/doc/en/articles/gjournal-desktop/article.html#UNDERSTANDING-JOURNALING "Your RAM size should fit in 30% of the journal provider's space. For example, if your system has 1 GB RAM, create an approximately 3.3 GB journal provider. (Multiply your RAM size with 3.3 to obtain the size of the journal)." What's the right size for journal on 143GB 15k rpm SAS disks on machine with 16GB of RAM? Based on second case, it will be more than 50 GB - one third of the size of disk. This is insane vasting. I have gjournal on few of our machines with size of journal set to 2GB on SATA disks in gmirror. Miroslav Lachman