From owner-freebsd-questions@FreeBSD.ORG Sun Mar 18 06:14:42 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 65CA416A404 for ; Sun, 18 Mar 2007 06:14:42 +0000 (UTC) (envelope-from jonathan@hst.org.za) Received: from ctb-mesg8.saix.net (ctb-mesg8.saix.net [196.25.240.78]) by mx1.freebsd.org (Postfix) with ESMTP id 0ACDC13C457 for ; Sun, 18 Mar 2007 06:14:41 +0000 (UTC) (envelope-from jonathan@hst.org.za) Received: from [172.16.0.1] (dsl-242-97-46.telkomadsl.co.za [41.242.97.46]) by ctb-mesg8.saix.net (Postfix) with ESMTP id 2C1C225E9; Sun, 18 Mar 2007 07:10:44 +0200 (SAST) From: Jonathan McKeown To: freebsd-questions@freebsd.org Date: Sun, 18 Mar 2007 07:12:19 +0200 User-Agent: KMail/1.8 References: <539c60b90703131212m731986b1p8603a86eca00d6b2@mail.gmail.com> <200703161208.49305.lists@jnielsen.net> <539c60b90703161248p7ddf9aefxf766ef482b6036cd@mail.gmail.com> In-Reply-To: <539c60b90703161248p7ddf9aefxf766ef482b6036cd@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200703180712.19467.jonathan@hst.org.za> Cc: Steve Franks Subject: Re: mirror without destroying existing contents X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 18 Mar 2007 06:14:42 -0000 On Friday 16 March 2007 21:48, Steve Franks wrote: > On 3/16/07, John Nielsen wrote: > > On Friday 16 March 2007 11:18, Steve Franks wrote: > > > I get the following: > > > > > > #gmirror label -v -b split -s 1024 data ad0 > > > can't store metadata on ad0: operation not permitted. > > > > That most likely means that you currently have a filesystem on ad0 > > mounted. If that's the case you should be glad that the OS was smarter > > than you. What steps had you taken prior to this? > > It appears to say in the manpage that you can do this on a disk with > an existing filesys - would you expect it to work if the disk is > unmounted first, then? The way to do this is potentially a little risky but I haven't had a problem with it yet after setting up several mirrors on live fileservers. There is a sysctl called kern.geom.debugflags: if you set this to 16 it will allow you to change the mounted filesystem. Bear in mind that since the metadata for the mirror is written to the last sector of the disk, there is a small risk of data loss: if that sector contains data it will be overwritten. There's a thorough howto by Ralph Engelschall, and an OnLamp article by Dru Lavigne, with more details: http://people.freebsd.org/~rse/mirror/ http://www.onlamp.com/pub/a/bsd/2005/11/10/FreeBSD_Basics.html Jonathan