From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bryn M. Reeves" Subject: Re: Chicken and egg problem with multipath-tools Date: Mon, 04 Mar 2013 10:54:15 +0000 Message-ID: <51347D57.9000908@redhat.com> References: <1362220999.44153.YahooMailClassic@web126202.mail.ne1.yahoo.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1362220999.44153.YahooMailClassic@web126202.mail.ne1.yahoo.com> 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 Cc: "Andrei B." List-Id: dm-devel.ids -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 03/02/2013 10:43 AM, Andrei B. wrote: > Hi, > > I've been trying to install multipath-tools on a couple of linux > servers with FC storage that I work with. They run Linux > Slackware. I've built from source, created an installable package > (Slackware style) and deployed it. > > I have discovered the following problem (chicken and egg style): > > - multipathd, AFAIK, should start before LVM, because if several > volumes need be assembled by LVM, they should exist before LVM > starts. The daemon is not required to discovery paths; just call "multipath" in the initramfs or early userspace to create mapped devices. Start the daemon later when you have writable root/var (or hack around it as I mentioned in my other reply). > - multipathd, AFAIK, should start before any service that has it's > data stored on the remote storage. No need usually. There is a small window where a path failure during boot will not be recoverable however in over five years supporting distros using this approach I've never seen that happen in practice (the timing is tight - it must be after mapping the device but before userspace gets going and it must require the daemon to intervene to reinstate paths to carry on). > I am not familiar [enough] with the inner workings of the startup > sequence on redhat/debian like systems. Slackware's startup > sequence is much simpler and I placed multipathd in file rc.S > (which is the first one called by init) right before LVM. Call multipath instead. Then start multipathd after your LVM devices are up and /var is writable. Regards, Bryn. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlE0fVcACgkQ6YSQoMYUY96cnQCeI/AYeKvu36kpdefUeLT4mNvw 1ycAoNQlgCK2D+fyHOjrEsPilzWMz+sn =qWjC -----END PGP SIGNATURE-----