On Thu, Mar 15, 2007 at 02:19:11AM -0700, Steve Langasek wrote: > > 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.
No, similar identifiers are listed in both. And for s390 the initramfs scripts
expects that the by-path name is used as root to be able to activate the
complete device.
> > | 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
320000020371a2f24 is the unique identifier of the disk.
| lrwxrwxrwx 1 root root 9 Mar 2 23:24
ccw-0.0.2900-zfcp-0x21000020371a2f24:0x0000000000000000 -> ../../sda
| lrwxrwxrwx 1 root root 10 Mar 2 23:24
ccw-0.0.2900-zfcp-0x21000020371a2f24:0x0000000000000000-part1 -> ../../sda1
| lrwxrwxrwx 1 root root 10 Mar 2 23:24
ccw-0.0.2900-zfcp-0x21000020371a2f24:0x0000000000000000-part2 -> ../../sda2
21000020371a2f24 is the identifier of the path to the disk. In this case there
exists two paths to the disk via one controller.
> > > 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...
But irrelevant in this case, as udev does not set links for dm devices in
by-uuid, they have a unique name per definition. (Yes, two lvm vgs with
the same name have weird effects ...)
> 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?
I'm not sure. You always get a race condition between the events for the two
devices.
Bastian
--
I have never understood the female capacity to avoid a direct answer to
any question.
-- Spock, "This Side of Paradise", stardate 3417.3
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