From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: Greater than 16 xvd devices for blkfront Date: Fri, 9 May 2008 00:34:13 +0100 Message-ID: <20080508233413.GA16160@redhat.com> References: <48209705.4030005@redhat.com> <20080507015502.GA2121@redhat.com> <20080507034726.GC2121@redhat.com> <20080507164031.GB18143@sequoia.sous-sol.org> <18466.51240.492762.405781@mariner.uk.xensource.com> <20080508153350.GO17453@sequoia.sous-sol.org> <48237B4A.4070808@goop.org> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <48237B4A.4070808@goop.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jeremy Fitzhardinge Cc: Chris Wright , Chris Lalancette , Ian Jackson , xen-devel List-Id: xen-devel@lists.xenproject.org On Thu, May 08, 2008 at 11:14:34PM +0100, Jeremy Fitzhardinge wrote: > Chris Wright wrote: > >Well, we don't actually need 202, or any minor numbers at all. The major > >is only needed for the case where xvd masquerades as IDE or SCSI. > >We ripped this wart out for upstream Linux. > > I'm considering putting it back in if it makes anyone's life easier. In > general using labels/uuids is the best way to make an installation > device-agnostic, but installers might have an easier time with a forged > scsi device or something. I mentioned it in passing to Al Viro, and he > was surprisingly non-insulting about the notion. > > > And the guest can happily > >dynamically allocate minor numbers on its own behalf. A disk discovery > >event can be completely dynamic, the admin just wouldn't be able to > >guarantee which minor slot gets allocated for a particular disk in > >a guest. We do have mount by label or UUID. > > > > That's true for filesystems which have already been initialized. But if > you're attaching 4 new devices to a guest and they appear at random > device nodes, how do you know which is which? Smell? Well there's /dev/disk/by-{path,id}. Now there's no udev rules to setup these links for Xen VBD (afaik), but we could arrange to have some suitable info used to provide a persistent path under either of those locations. Dan. -- |: Red Hat, Engineering, Boston -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|