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I have a system with two MegaRAID RAID-6 partitions which were turned into a single RAID-0 system using Linux software RAID, although not by me. I lost the /md* partition when upgrading the system, but the /dev/sda1 and /dev/sdb1 hardware RAID partitions are still there. I cannot mount either of the hardware raid partitions. Can I recover the /md* partitions using mdadm or dmraid without losing everything?

Here's the info on both of the partitions that were part of the RAID 0 configuration:

    mdadm --examine /dev/sda1
/dev/sda1:
          Magic : a92b4efc
        Version : 0.90.00
           UUID : 754cf49f:6e88dcc2:25005497:2b83f9e9
  Creation Time : Tue Mar 20 22:28:11 2012
     Raid Level : raid0
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 3

    Update Time : Tue Mar 20 22:28:11 2012
          State : active
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 7c59057a - correct
         Events : 1

     Chunk Size : 64K

      Number   Major   Minor   RaidDevice State
this     0       8       33        0      active sync   /dev/sdc1

   0     0       8       33        0      active sync   /dev/sdc1
   1     1       8       49        1      active sync   /dev/sdd1

mdadm --examine /dev/sdb1
/dev/sdb1: 
          Magic : a92b4efc
        Version : 0.90.00
           UUID : 754cf49f:6e88dcc2:25005497:2b83f9e9
  Creation Time : Tue Mar 20 22:28:11 2012
     Raid Level : raid0
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 3

    Update Time : Tue Mar 20 22:28:11 2012
          State : active
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 7c59058c - correct
         Events : 1

     Chunk Size : 64K

      Number   Major   Minor   RaidDevice State
this     1       8       49        1      active sync   /dev/sdd1

   0     0       8       33        0      active sync   /dev/sdc1
   1     1       8       49        1      active sync   /dev/sdd1

Note that before the upgrade the two partitions were sdc1 and sdd1, while after the upgrade they're sda1 and sdb1.

  • 1
    Sorry about my novice mistake. I solved the problem myself by actually reading the mdadm documentation and spinning up on its various capabilities. Reassembling the two hardware RAID-6 arrays into a software RAID-0 array was as easy as entering: mdadm --assemble /dev/md3 /dev/sda1 /dev/sda2 – Steven Baum Mar 27 '17 at 15:11
  • You could add that as a (self)-Answer! – Jeff Schaller Mar 27 '17 at 16:04
  • @StevenBaum fantastic news, I'm sure! Please do add it as an answer (and then accept it when you can) to help others potentially in a similar situation. – roaima Mar 27 '17 at 16:23

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