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Re: md raid 5 not working



Kanwar Ranbir Sandhu wrote:
On Sat, 2009-12-26 at 15:28 -0500, Kanwar Ranbir Sandhu wrote:
My Linux RAID skills/experience aren't that deep, so I'm not sure how to
fix this.  I'd appreciate any pointers.

Some details:

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       60801   488384001   fd  Linux raid autodetect

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1       60801   488384001   fd  Linux raid autodetect

   Device Boot      Start         End      Blocks   Id  System
/dev/sde1               1       60801   488384001   fd  Linux raid autodetect

Solved my problem!

As you can see here, the md superblock is on the first primary partition
of each of these drives.  But, Linux wasn't seeing these partitions.  A
simple 'ls -l /dev/sd*' only showed me /dev/sdb, /dev/sdd, and /dev/sde.
The reason I provided mdadm details on these drives was because I
couldn't see /dev/sdb1, etc.  I couldn't give md information on the
partitions.

I realized I had once used the entire drives in a md RAID 5 set instead
of building the RAID 5 on partitions.  I had outdated md superblocks
on /dev/sd[bde]!  I suppose when I rebuilt the array properly, I didn't
wipe the drives completely.  Basically, the old md superblocks were
confusing the kernel.

To fix this, I ran the following from the rescue CD:

mdadm --zero-superblock --force /dev/sdb
mdadm --zero-superblock --force /dev/sdd
mdadm --zero-superblock --force /dev/sde

When I rebooted, /dev/md3 was detected properly and came up without any
problems.  Sweet!

Thanks to everyone that replied.  I didn't think I could solve this one
on my own, but the man page + my realization of what was going on helped
immensely.

For future reference there is also the linux-raid mailing list which handles issue regardless of release.

--
Bill Davidsen <davidsen tmr com>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot


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