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Re: AW: [Xen-users] debian Lenny -> Squeeze domU mdX software raidmigration - failed to assemble arrays


It really depends, personally if you are specifying the targets of the
disks in the xen config file the device will be persistent across any
amount of reboots and addition of new disks so the use of UUIDs or
LABELs isn't really all that beneficial in my view.
Especially if you want the ability to clone the volume or back it up
via mounting the disk and taring it up etc.
I still find good old fashioned paths the best way: /dev/xvda1 etc.


On 5 May 2011 20:10, Simon Hobson <linux@xxxxxxxxxxxxxxxx> wrote:
> netz-haut - stephan seitz wrote:
>> to make transitions more convenient, I've done this by using uuid instead
>> of device names.
>> If you ls -l /dev/disk/by-uuid inside your domU, you'll see something like
>> lrwxrwxrwx 1 root root 10  5. Mai 07:38
>> 39a2a64b-0716-47ad-92f4-a7437cac54ee -> ../../sda2
>> lrwxrwxrwx 1 root root 10  5. Mai 07:38
>> e8b97b59-a790-417c-8231-fe8da8b6e6ee -> ../../sda1
>> In /etc/fstab inside the domU, '/dev/sda2' would be replaced by
>> 'UUID=39a2a64b-0716-47ad-92f4-a7437cac54ee' and '/dev/sda1' by
>> 'UUID=e8b97b59-a790-417c-8231-fe8da8b6e6ee'
>> If pvgrub or pygrub is used, the devicename needs to be replaced inside
>> the domU in /boot/grub/menu.lst from e.g. 'root=/dev/sda2' to
>> 'root=UUID=39a2a64b-0716-47ad-92f4-a7437cac54ee'
>> If, like in your case, the domU kernel is directly booted by a cfg
>> statement, the root statement needs to be changed in the cfg file by using
>> the the same formatting as in the menu.lst above.
>> Now, it doesn't matter any longer if the device is called xvda or sda or
>> (ancient but possible) hda.
> Would using labels be more convenient ? At least on ext2/3, dunno about
> others.
> If you should move a guest to another host, or rebuild it's filesystem for
> any reason, setting a label on the filesystem is probably easier than
> finding the places (multiple - Dom0 and DomU) places the UUID has been used.
> --
> Simon Hobson
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
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