From mboxrd@z Thu Jan 1 00:00:00 1970 From: malahal@us.ibm.com Subject: Re: Use LVM on /dev/mapper/diskname Date: Mon, 19 Nov 2007 09:22:19 -0800 Message-ID: <20071119172219.GA22727@us.ibm.com> References: <1195480602.6074.3.camel@sanderbal> <47419854.2000508@linpro.no> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <47419854.2000508@linpro.no> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Tore Anderson Cc: device-mapper development List-Id: dm-devel.ids Tore Anderson [tore@linpro.no] wrote: > * S. J. van Harmelen > > > I have a couple of LUN's that are handled by the multipath driver. > > This works great, but now I want to use LVM so I can take snapshots > > of one LUN to another LUN. > > > > Can someone tell me how to do this? > > > > When I do pvcreate /dev/mapper/diskname I get an error that the disk > > is already part of an volume group. But I sertainly did not configure > > that. > > > > Can it be that the multipath driver of devmapper did that? > > If you have a PV signature on the volume, LVM might have used one of the > paths instead of using the multipath'ed device under /dev/mapper. You > should be able to check this by running the command "pvs" - it should > list all the detected PVs on your system. If LVM uses single pathed disks like /dev/sda, then multipath can't use the same path to make a multipathed device, right? My guess is that /dev/mapper/multipath-name is indeed part of the LVM in your case. I would like to know what happened otherwise. Thank you. --Malahal.