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I have a RAID 5 array, md0, with three full-disk (non-partitioned) members, sdb, sdc, and sdd. My computer will hang during the AHCI BIOS if AHCI is enabled instead of IDE, if these drives are plugged in. I believe it may be because I'm using the whole disk, and the AHCI BIOS expects an MBR to be on the drive (I don't know why it would care).

Is there a way to convert the array to use members sdb1, sdc1 and sdd1, partitioned MBR with 0xFD RAID partitions?

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My gut feeling is that while you can rebuild it, you won't be able to convert or migrate your current array. If you have other disks lying around, it'd be worth testing the theory before you do anything drastic. But I'm certainly not an expert on linux soft arrays. – SilverbackNet Dec 23 '10 at 2:16
up vote 3 down vote accepted

It might be possible like this:

  1. remove first disk from the array (mark it as faulty & remove)
  2. create RAID partition on the removed disk
  3. add newly created RAID partition back to the array
  4. wait until the raid is finished with rebuilding (very important! :)
  5. repeat steps 1..4 for the remaining disks

As usual, make sure that you have a good backup before doing it.

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Though I haven't been able to try it, because since asking the question I've recreated a new 3TB (4x 1TB) RAID5 array from scratch. However, your answer looks very possible. – Delan Azabani Dec 31 '10 at 0:59

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