From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tore Anderson Subject: Re: Use LVM on /dev/mapper/diskname Date: Mon, 19 Nov 2007 15:06:12 +0100 Message-ID: <47419854.2000508@linpro.no> References: <1195480602.6074.3.camel@sanderbal> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1195480602.6074.3.camel@sanderbal> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids * 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 this was the problem, you can avoid it by instructing LVM to not scan SCSI devices directly, by adding a line in /etc/lvm/lvm.conf like this: device { filter = [ "a|^/dev/mapper/.*|", "r|.*|" ] } This will make LVM only look at devices in /dev/mapper/ as possible PV candidates, ignoring all other devices. Beware if you have a PV on the internal drives though, you might want to have something like this instead in that case (if that PV is on /dev/sda2, for instance): filter = [ "a|^/dev/mapper/.*|", "a|^/dev/sda2$|", "r|.*|" ] Make sure lvm.conf makes its way into the initramfs if you start the LVM stuff there. I know Ubuntu doesn't include this file by default, at least. Regards -- Tore Anderson