From owner-freebsd-geom@FreeBSD.ORG Sun Mar 23 11:35:38 2008 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 9F779106564A for ; Sun, 23 Mar 2008 11:35:38 +0000 (UTC) (envelope-from 000.fbsd@quip.cz) Received: from elsa.codelab.cz (elsa.codelab.cz [91.103.162.4]) by mx1.freebsd.org (Postfix) with ESMTP id 57BD08FC1F for ; Sun, 23 Mar 2008 11:35:37 +0000 (UTC) (envelope-from 000.fbsd@quip.cz) Received: from localhost (localhost.codelab.cz [127.0.0.1]) by elsa.codelab.cz (Postfix) with ESMTP id 1AA5119E027; Sun, 23 Mar 2008 12:35:36 +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 ESMTP id B97F919E019; Sun, 23 Mar 2008 12:35:31 +0100 (CET) Message-ID: <47E64097.4080604@quip.cz> Date: Sun, 23 Mar 2008 12:35:51 +0100 From: Miroslav Lachman <000.fbsd@quip.cz> User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.12) Gecko/20050915 X-Accept-Language: cz, cs, en, en-us MIME-Version: 1.0 To: Arnaud Houdelette References: <47DD1C9A.1020208@tzim.net> In-Reply-To: <47DD1C9A.1020208@tzim.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-geom@freebsd.org Subject: Re: Geom_Raid5 best practices ? 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: Sun, 23 Mar 2008 11:35:38 -0000 Arnaud Houdelette wrote: > I use geom_raid5 for my home NAS for nearly 1 year. > No problems so far (but just the fact I had to patch ata-disk.c to > modify the IO timeout in order to be able to use ataidle). > > Since I updated to 7.0-RELEASE, I was wondering if I should use gjournal > on the raid5 array. > The array's purpose is to store music (2-10 MB) and video (300MB to 8GB) > files. > > My system is as it follow : > - USB key for base system (power/sound efficient) > - 120 GB Pata disk for temporary downloads, /usr/src, ports and obj > - 4x250 GB sata disks for mass storage (so 750GB usable space). > > I currently use plain UFS+SU on every FS, and daily snapshots on the > raid5 one. > GJournal should protect the raid5 UFS from destruction by bad power > failures/kernel crashes, but with what performance impact ? Is the risk > of complete FS crash really important with only SU ? (loss of data > written at the time of the crash is no big deal, nor waiting for a fsck > to complete, as long as I can recover most of the data previously stored) > > But as the gjournal first introduction showed a big performance drop on > big files (they apparently have to be written twice), I was really > wondering if I should use a journal on the file system ? > If so, where should I put the journal on, and wich journal size should I > use ? I am not too experienced with gjournal, I think the best way for you is gjrounaled RAID5 (data) and journal on another disk (your 120GB) with size calculated from RAID5 write throughput and kern.geom.journal.switch_time (10 seconds by default) plus some reserve. (place journal partition in start of the disk for better throughput) This settup will give you the best performance you can achieve with gjournal. Miroslav Lachman