Bug#389881: RC-ness of this bug
On Thu, Mar 15, 2007 at 08:56:39AM +0100, Bastian Blank wrote:
> On Wed, Mar 14, 2007 at 04:57:51PM -0700, Steve Langasek wrote:
> > > >, it changes if you change the SCSI/IDE bus address
> > > > of the drive
> > > the same applied in the old hd? and sd? days, drives names changing when
> > > you change thier IDE/SCSI ids is something admins expect and are used to.
> > Um. Have you ever even used SCSI?
> Someone which uses scsi-over-fc have much better identification, the wwnn,
> which is used in by-id:
So it's used in by-id, but not in by-path, right? Hence this is still an
argument against by-path.
> | $ ls -al /dev/disk/by-id/scsi-320000020371a*
> | lrwxrwxrwx 1 root root 9 Mar 2 23:24 /dev/disk/by-id/scsi-320000020371a2f24 -> ../../sda
> | lrwxrwxrwx 1 root root 10 Mar 2 23:24 /dev/disk/by-id/scsi-320000020371a2f24-part1 -> ../../sda1
> | lrwxrwxrwx 1 root root 10 Mar 2 23:24 /dev/disk/by-id/scsi-320000020371a2f24-part2 -> ../../sda2
> > Well, some of us have, and I don't think any admin of such systems enjoys
> > having to fix /etc/fstab by hand.
> Also many fc-users wants multipath anyway, which also uses the wwnn for
> identification.
True; though supported multipath implementations sadly vary with vendor.
> > Using dd to back up a partition to another isn't a very sensible backup
> > schema anyway. I think more people move PCI devices than back up systems
> > this way...
> It is widely used in form of snapshots.
Yes, snapshots are fairly common, and at least in the case of a power outage
/ system crash you'd have to worry about them being around on reboot. Hmm,
having the system unable to mount a root fs at all on reboot would be even
worse for recovery than having it accidentally mount a snapshot, which is
already bad enough...
> > What does the kernel do when it finds two filesystems with colliding uuids?
> > Ideally, to avoid any accidents, it should rename them both. With that fix
> > (if indeed it needs fixing), I think all the main problems of by-uuid go
> > away.
> It does nothing special. This is completely userspace. And current udev just
> uses the last seen one, which is usualy the removable device in this case.
Right. Do you think it would be sensible to rename both devices on
collision? Do you think that would be sufficient for making by-uuid a safe
default?
--
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
vorlon@debian.org http://www.debian.org/
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