Hi again,
Sorry for the delay (Christmas vacation, ++). I still have the problem
though.
My attempt to re-create /dev/sdb1 by fdisk'ing it again and adding it to
the array failed. That is, mdadm started re-constructing the array, and
that succeeded, but when I rebooted /dev/sdb1 was missing again :/
Neil Brown wrote:
If a partition start at an offset in the device which is a multiple of
64K, and ends at the end of the device, then both the partition and
the whole device will appear to have the same superblock. This can
cause confusion.
I think you are on to something here! I did partition all my disks with
just one partition, starting on the first block and taking up all the
remaining space, and set it to type Linux RAID auto detect.
Here's the output of the fdisk -pu and mdmadm -E commands before running
blockdev:
http://pastebin.com/f4cad67ea
http://pastebin.com/f34be2b86
It seems that mdadm thinks sd[bc] are part of the array directly
somehow, but for sd[def] the partition itself is in the array, which I
guess supports your suspicion?
Here's the output after running blockdev --rereadpt /dev/sdc :
http://pastebin.com/f725ee0c3
Suddenly mdadm -E /dev/sdc* shows info for both sdc and sdc1, and guess
what? /dev/sdc1 is back as a device node :)
So is this a case of the problem you described about
superblock-confusion? If so, is it fixable?
Thank you so much for your help in this! I really do feel I'm one big
step closer to solving this!
Tor Arne
Tor Arne Vestbø wrote:
So is this a case of the problem you described about
superblock-confusion? If so, is it fixable?
Btw, I cloned mdadm from your site, so I have an updated version now. I
haven't installed it yet, in case it can damage the existing RAID, but
if there are any tests I can run with the updated version I'm ready for
them :)
Tor Arne
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Tor Arne Vestbø wrote:
Neil Brown wrote:
quoted
If a partition start at an offset in the device which is a multiple of
64K, and ends at the end of the device, then both the partition and
the whole device will appear to have the same superblock. This can
cause confusion.
I think you are on to something here! I did partition all my disks with
just one partition, starting on the first block and taking up all the
remaining space, and set it to type Linux RAID auto detect.
[snip]
So is this a case of the problem you described about
superblock-confusion? If so, is it fixable?
It appears it is :)
For googlability, here's what I did:
Changed the DEVICE line in my mdadm.conf from:
DEVICE partitions
to
DEVICE /dev/sd[bcdef]1
Now the array is assembled correctly at boot.
I'm still confused why the device nodes went missing as a result of the
failed assembly earlier, but that's a minor issue I can live with :)
Tor Arne
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Tor Arne Vestbø wrote:
Changed the DEVICE line in my mdadm.conf from:
DEVICE partitions
to
DEVICE /dev/sd[bcdef]1
Now the array is assembled correctly at boot.
A safer way of acheiving this is to list the array in mdadm.conf by
UUID, which will guarantee all the correct devices are used - sd devices
can move around under some conditions.
eg.
ARRAY /dev/md1 level=raid1 num-devices=2
UUID=f6bd7495:52288189:40f44282:1c220686
ARRAY /dev/md0 level=raid1 num-devices=2
UUID=f7d720fe:a5d0724c:c9bd10fa:a496ed51
Note each ARRAY entry and UUID are entered as a single line.
Regards,
Richard
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