Partitions missing on startup

[KingPong]

Hello,

I have a new OpenSuSE 10.3 server that I configured a RAID-1 root partition on. The system boots successfully, but my RAID volume always starts in degraded mode, because the second partition (sdb2) does not exist in /dev.

This one really confuses me. I created the partition table on sdb as an exact copy of sda -- a 200M partition for /boot, and the rest for RAID. The boot partition on sdb is unused (although I keep a copy of my "live" boot partition on it).

Could you please help me? Lots of details are below. If you need any others, please ask.

The kernel is seeing the partitions. Excerpt from dmesg:

sd 1:0:0:0: [sdb] 976773168 512-byte hardware sectors (500108 MB)
sd 1:0:0:0: [sdb] Write Protect is off
sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
 sdb: sdb1 sdb2
sd 1:0:0:0: [sdb] Attached SCSI disk

fdisk also sees the partitions:

# fdisk -l /dev/sdb

Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x0005e7eb

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          26      208813+  83  Linux
/dev/sdb2              27       60801   488175187+  fd  Linux raid autodetect

But for some reason, the device nodes are not being created:

# ls -l /dev/sdb*
brw-r----- 1 root disk 8, 16 May 31 16:28 /dev/sdb
# grep sdb /proc/partitions
   8    16  488386584 sdb
#

And mdadm can't start the array properly: (from boot.msg)

Creating device nodes with udev
mdadm: failed to add /dev/sdb2 to /dev/md0: No such device or address
mdadm: /dev/md0 has been started with 1 drive (out of 2).

If I use fdisk to re-write the partition table on the live system, I can then add sdb2 to my RAID array and it will resync. This is good until the next reboot, at which point the partition is missing again, and I have to resync all over again.

# fdisk /dev/sdb
(snip)
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          26      208813+  83  Linux
/dev/sdb2              27       60801   488175187+  fd  Linux raid autodetect

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
# mdadm /dev/md0 -a /dev/sdb2
mdadm: re-added /dev/sdb2
# cat /proc/mdstat
Personalities : [raid1] [raid0] [raid6] [raid5] [raid4] [linear] 
md0 : active raid1 sdb2[2] sda2[0]
      488175048 blocks super 1.0 [2/1] [U_]
      [>....................]  recovery =  0.1% (621824/488175048) finish=156.7min speed=51818K/sec
      bitmap: 19/466 pages [76KB], 512KB chunk

unused devices: <none>

[KingPong]

Can anyone think of any reason that sdb1 and sdb2 would be listed in dmesg but not in /dev?

[thecheatah]

Were you able to resolve the issue?

[KingPong]

I could have sworn there were more posts on this thread.

I don't think I ever satisfactorily resolved the problem. If memory serves, I just replaced the disk with a spare.

In retrospect, I may have just needed to zero the superblock (mdadm --zero-superblock).

[thecheatah]

For me, after upgrade Ubuntu from 9.04 to 9.10 two of my disks' partitions disappeared. I have 5 drives. 2 are raided and used as /home and 2 are for backups.

The weird part was that BOTH /home drives dont show there partitions in the /dev dir. They show up in fdisk -l and in dmesg. The other weird part is that if I use the Ubuntu 9.04 Live CD the drives and the partitions come up. I actually backed up my /home disks to my backup disks using the live cd so I am not worried about the data on them.

I have also tried Fedora 11 and it also fails to find the partition. There appears to be some sort of an upgrade in the kernel (or other disk related software) that is causing this problem for me.

I can reformat the disks and copy the data back, but then I will always be worred about losing my data due to upgrades.

Thanks for the reply.