On 10.01.2012 07:12, Gilbert Kowarzyk wrote:
# mdadm --examine --scan /dev/sdc1
=================================>
ARRAY /dev/md/9 metadata=1.1 UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
name=xyz.homelinux.com:9
<=================================
# mdadm --examine --scan /dev/sdd1
=================================>
ARRAY /dev/md/9 metadata=1.1 UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
name=xyz.homelinux.com:9
<=================================
# mdadm --detail --scan
=================================>
ARRAY /dev/md/xyz.homelinux.com:9 metadata=1.1
name=xyz.homelinux.com:9 UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
<=================================
# blkid
=================================>
/dev/md127: UUID="c301cf13-cfaf-4f56-887e-c648caf5a931" TYPE="ext4"
<=================================
in /etc/fstab I have:
=================================>
UUID=c301cf13-cfaf-4f56-887e-c648caf5a931 /DATA ext4 defaults 1 2
<=================================
and in /etc/mdadm.conf I have:
=================================>
ARRAY /dev/md/xyz.homelinux.com:9 metadata=1.1
name=xyz.homelinux.com:9 UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
<=================================
To me, the line that looks suspicious is the one we get from "mdadm
- --detail --scan". All the devices that "look right" say "ARRAY
/dev/md/X" where X is a number.
I fixed this temporarily by stopping the array and re-assembling it with:
mdadm --assemble /dev/md9 --name=9 --update=name /dev/sdc1 /dev/sdd1
You updated name stored in the metadata, and assembled the array
explicitly requesting particular standard name. But the names directly
under /dev are managed/assigned by udev.
As the /dev/md9 was explicitly given in this form, the MD_DEVNAME was
not present in 'mdadm --detail --export' output, thus /dev/md/9 was not
created by mdadm's udev rules - but it would have been if you had done
mdadm --assemble /dev/md/9 ...
Then the mdadm --detail --scan line says:
ARRAY /dev/md/9 metadata=1.1 name=xyz.homelinux.com:9
UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
... which makes more sense to me (it looks like the other ones.
Yet, when I reboot the computer this "temporarily fixed" array returns
to /dev/md127.
But you should have proper, permanent name (as a symlink) under /dev/md/
Autoassembly (be it -I used with modern mdadm's udev rules) or -A will
try to honor the device name if the name is in standard format, so for
mdadm.conf with ARRAY /dev/md/9 ... - you will (usually) get /dev/md9 -
but this it's not really worth chasing after or relying on (and what if
the name is already taken ?).
Just write:
ARRAY /dev/md/somename UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
ARRAY somename UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
in which case 'somename' will be created under /dev/md/ regardless of
the name stored in the metadata, or just
ARRAY UUID=0fa7f737:7806ca61:fb89edd6:14aa351a
so the metadata (without hostname prefix) will be used.
So to sum it up - if '9' is what you're after - then the ARRAY line with
just UUID is all you should be needing - and you should always get
/dev/md/9 (pointing to something else assigned dynamically).
If udevd is not running (hardly interesting case anymore), then mdadm
will fall back to the pre-udev behavior and setup the nodes itself,
though the rules are slightly different then.
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