`mdadm` comamnd is unable to assemble an existing array.

Issue

• mdadm comamnd is unable to assemble an existing array. mdadm --assemble --scan returns "mdadm: /dev/md0 assembled from 2 drives - not enough to start the array."

  Array information is as follows

  ARRAY /dev/md0 devices=/dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sde1
  

  And mdadm --examine /dev/sdx1 returns clean and active for each disk ...

  [root@hostname ~]# mdadm --examine /dev/sda1
  /dev/sda1:
        Magic : a92b4efc
      Version : 0.90.00
         UUID : 35413b36:5583131c:0e88505a:69de3bee
  Creation Time : Thu Aug 18 17:18:37 2011
   Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Array Size : 2930279808 (2794.53 GiB 3000.61 GB)
  Raid Devices : 4
  Total Devices : 4
  Preferred Minor : 0
  
  Update Time : Tue Nov  4 12:39:56 2014
        State : clean
  Active Devices : 4
  Working Devices : 4
  Failed Devices : 0
  Spare Devices : 0
     Checksum : 89364046 - correct
       Events : 446
  
       Layout : left-symmetric
   Chunk Size : 64K
  
    Number   Major   Minor   RaidDevice State
  this     0       8        1        0      active sync   /dev/sda1
  
  0     0       8        1        0      active sync   /dev/sda1
  1     1       8       17        1      active sync   /dev/sdb1
  2     2       8       33        2      active sync   /dev/sdc1
  3     3       8       65        3      active sync   /dev/sde1
  [root@hostname ~]# mdadm --examine /dev/sdb1
  /dev/sdb1:
        Magic : a92b4efc
      Version : 0.90.00
         UUID : 35413b36:5583131c:0e88505a:69de3bee
  Creation Time : Thu Aug 18 17:18:37 2011
   Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Array Size : 2930279808 (2794.53 GiB 3000.61 GB)
  Raid Devices : 4
  Total Devices : 4
  Preferred Minor : 0
  
  Update Time : Tue Nov  4 12:39:56 2014
        State : clean
  Active Devices : 4
  Working Devices : 4
  Failed Devices : 0
  Spare Devices : 0
     Checksum : 89364058 - correct
       Events : 446
  
       Layout : left-symmetric
   Chunk Size : 64K
  
    Number   Major   Minor   RaidDevice State
  this     1       8       17        1      active sync   /dev/sdb1
  
  0     0       8        1        0      active sync   /dev/sda1
  1     1       8       17        1      active sync   /dev/sdb1
  2     2       8       33        2      active sync   /dev/sdc1
  3     3       8       65        3      active sync   /dev/sde1
  [root@hostname ~]# mdadm --examine /dev/sdc1
  /dev/sdc1:
        Magic : a92b4efc
      Version : 0.90.00
         UUID : 35413b36:5583131c:0e88505a:69de3bee
  Creation Time : Thu Aug 18 17:18:37 2011
   Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Array Size : 2930279808 (2794.53 GiB 3000.61 GB)
  Raid Devices : 4
  Total Devices : 4
  Preferred Minor : 0
  
  Update Time : Thu Oct 23 15:10:57 2014
        State : clean
  Active Devices : 4
  Working Devices : 4
  Failed Devices : 0
  Spare Devices : 0
     Checksum : 892683a7 - correct
       Events : 434
  
       Layout : left-symmetric
   Chunk Size : 64K
  
    Number   Major   Minor   RaidDevice State
  this     2       8       33        2      active sync   /dev/sdc1
  
  0     0       8        1        0      active sync   /dev/sda1
  1     1       8       17        1      active sync   /dev/sdb1
  2     2       8       33        2      active sync   /dev/sdc1
  3     3       8       65        3      active sync   /dev/sde1
  [root@hostname ~]# mdadm --examine /dev/sde1
  /dev/sde1:
        Magic : a92b4efc
      Version : 0.90.00
         UUID : 35413b36:5583131c:0e88505a:69de3bee
  Creation Time : Thu Aug 18 17:18:37 2011
   Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Array Size : 2930279808 (2794.53 GiB 3000.61 GB)
  Raid Devices : 4
  Total Devices : 4
  Preferred Minor : 0
  
  Update Time : Thu Oct 23 15:10:57 2014
        State : clean
  Active Devices : 4
  Working Devices : 4
  Failed Devices : 0
  Spare Devices : 0
     Checksum : 892683c9 - correct
       Events : 434
  
       Layout : left-symmetric
   Chunk Size : 64K
  
    Number   Major   Minor   RaidDevice State
  this     3       8       65        3      active sync   /dev/sde1
  
  0     0       8        1        0      active sync   /dev/sda1
  1     1       8       17        1      active sync   /dev/sdb1
  2     2       8       33        2      active sync   /dev/sdc1
  3     3       8       65        3      active sync   /dev/sde1