mdadm fails to start the raid array with error - 'not enough to start the array.'

Solution Verified - Updated -

Issue

  • We have configured software RAID5 array using 3 disks. There were some issue in the connectivity to 2 disks used for raid array, due to which mdraid marked them as failed/faulty. Executing mdadm --examine /dev/sdx command with the ramaining disk returns following:
$ mdadm --examine /dev/sdb
[...]
     Layout : left-symmetric
     Chunk Size : 64K
      Number   Major   Minor   RaidDevice State
this     1       8       16        1      active sync   /dev/sdb
   0     0       0        0        0      removed                           <---
   1     1       8       16        1      active sync   /dev/sdb
   2     2       0        0        2      faulty removed                    <---
  • The connectivity issues with 2 failed disks are now resolved, and we are trying to reassemble the array but mdadm fails with following error
$ mdadm -A /dev/md0
mdadm: /dev/md0 assembled from 1 drive - not enough to start the array.

Environment

  • Red Hat Enterprise Linux 5
  • RAID 5 array configured using mdraid

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