Linux RAID autodetect partitions go missing from /dev, but fdisk can see them

Hi all,

I have a very strange problem that I've been trying to debug for days now. I'm hoping someone on this list may have ran into this before, or have any tips on how I can continue debugging this, because I have to admit I'm a little lost...

I had a RAID5 with four drives and one spare, /dev/sd[bcde]1 + /dev/sdf1, and everything was working fine, until one day one of the drives in the array (sdb) no longer had a partition (sdb1). Letting the spare take over I ignored this for a few days, but then it happened again, this time with sdc. Kernel is 2.6.22.17, and I've compiled all raid support in. The symptoms are:

- The kernel seems to detect the partitions (lines 396 and 407 in the
dmesg [1])

- But once the boot process finishes and the RAID is started, there is
no longer any sdc1 or sdb1, so the RAID fails to start (lines 550-576 in dmesg [1])

- Running fdisk -l shows that the drives in question (sdb and sdc) do
have similar partitions as the other working drives, namely one Linux RAID autodetect partition each (see command output [2])

- But, the partitions are missing from /proc/partitions (see [3])

- Manually adding device nodes using mknod works, but doing file -sL
on the device gives "writable, no read permission", even though permissions are the same as the other sd* nodes in /dev

- Running 'partprobe -s' successfully finds the two missing partitions
and adds device nodes, and the nodes can be 'file -sL'ed, but when trying to assemble the array again with these new nodes in the system, I'm told that sdc1 is not found, and after the --assemble is done, the device nodes are once again missing (!) see [4]

- I've tried using the 'dmraid' command to look for fakeraid
partitions or meta data on the drives, which I was told could mess up the auto-detection of Linux software ride partitions, but could not find any issues.

As you can tell I've exhausted all my current options, so any help on what I could try next would be very much appreciated. I am especially curious as to why I lose the partitions when mdadm tries to assemble the array?

Thanks!

Tor Arne Vestbø

[1] http://pastebin.com/m15b9c275   dmesg
[2] http://pastebin.com/f50fb323a   fdisk -l
[3] http://pastebin.com/f4547c2ca   cat /proc/partitions
[4] http://pastebin.com/m4475c9ae   partprobe + mdadm --assemble

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