[dm-devel] Multipath device naming

[Guido Guenther]

Hi,
there seems to be little to no consensus on how the device naming of
multipathed devices should look like across distributions:

The current kpartx udev rule in the upstream source (the patch came from
Hannes) sets the device naming to: /dev/mapper/<wwid>-part[0-9]+ so I
assume this is what SuSE uses (or intends to use in the future).
Redhat/Fedora seems to skip the '-p -part' so partitions look like:
/dev/mapper/<path>p?[0-9]+. The 'p' being used if <path> already ends in
a number. No distro seems to use user_friendly_names=yes by default (in
which case <...> would become mpath[0-9]+). And there's /dev/disk/by-name/
of course which would use the WWID if alias wasn't set.

All this gives bootloaders like grub and installers a hard time (every
distro seems to have similar patches to grub-install, etc.). I wonder if
it wouldn't make sense to adopt a common naming scheme across
distributions and probably reserve the whole
/dev/mapper/mpath[0-9]+p[0-9]+ and /dev/mapper/mpath[0-9]-part[0-9]+
namespaces for multipath devices? Otherwise it might become increasingly
harder for tools like parted to find out the partitions of a device
(without the almost very same set of patches that every distro carries
around). Any thoughts?
Cheers,
 -- Guido