Convert GPT to MBR (non-destructively via iPartition)

Now the question is: Can I non-destructively convert the RAID’s partitioning system from GPT to MBR? Non destructively here means I don’t have to wipe the disk (through reformatting etc) and recover the data from backup. The answer is YES! The Mac-based iPartition app does exactly that.

iPartition 3.1.1 (154) did it fine, taking around 6 or 7 hours.


  1. Mac OS: Start iPartition
  2. iPartition: Update, from 3.1.0 (153) upgraded to 3.1.1 (154) which is the first version able to do nondestructive partition system conversion.
  3. iPartition: Select disk device (in my case it was disk3)
  4. iPartition: Shrink the partitions. This is needed because conversion requires some free “workspace” area and also (it seems in retrospect) MBR is less efficient than GPT hence less disk available for actual data. For each partition, specify the shrink by clicking (activating) the partition then dragging its handle round to minimum size.
  5. iPartition: Convert, from GPT to PC(MBR).
  6. iPartition: Grow the partitions. As before, drag the handles. Chose to make them each 50% of available space, resulting in about 1TB apiece.
  7. All the above is just specifying the job. Press GO to begin actually doing the processes.
  8. Took about 6 or 7 hours…

Leave a Reply

You must be logged in to post a comment.