bizarre, j'arrive plus à le monter

[root@test-rhel4 ~]# mount /dev/md0 /mirror
/dev/md0: Invalid argument
mount: /dev/md0: can't read superblock

[root@test-rhel4 ~]# fsck /dev/md0
fsck 1.35 (28-Feb-2004)
e2fsck 1.35 (28-Feb-2004)
fsck.ext2: Invalid argument while trying to open /dev/md0

The superblock could not be read or does not describe a correct ext2
filesystem. If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device>