Richard Gooch writes:
> But you're really just moving the problem, since now you have to
> configure LVM/MD to say where the real devices are. And they can shift
> around (which is where this dicussion started).
If the kernel/devfs knows enough to scan each partition for a filesystem
UUID/label/serial number, it can also look for a PVID (LVM physical volume
UUID) at the start of a partition just as easily. The kernel would put
these in the same place as all of the other filesystem partition id's.
The LVM user-space code doesn't need to scan the disks anymore - it is
handled dynamically by the kernel. The LVM userspace code only looks
for /devfs/partition/uuid/a1e2a40a-5e03-11d3-80a3-d445fed6a62c (which
is a symlink/reference to the correct physical disk/partition no matter
where it is connected) to find a PV it is looking for. How the PVs are
put together into a volume group is already stored in config files in
/etc/lvm. The only issue at this point is that LVM has to scan all of
the disks looking for identifiers.
Once a filesystem is in LVM, you always mount it by the LV name, so it
is irrelevant where it is physically located, as LVM handles this for you.
In the LVM case, you don't need to mount by filesystem label/uuid anymore
to avoid device renaming. You would only need to keep mounting by label/uuid
for filesystems that do not live inside LVM.
Cheers, Andreas
--
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert
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