I have a 3TB disk which had a 128MB Microsoft basic data partition at the beginning, and the rest was a large ~2.7TB ntfs partition. I recently converted this disk from GPT to MBR, and the second large partition is now invisible in gdisk. I have read that MBR cannot handle partitions over 2.2TB, so I imagine when I converted the disk, the large 2.7TB partition was lost in some way.

Is it possible to recover this partition?

When I load gdisk on this drive I get the error message

Found invalid GPT and valid MBR; converting MBR to GPT format in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by typing 'q' if you don't want to convert your MBR partitions to GPT format!

From this message I gathered that the disk will simply be converted to GPT with existing data being kept in tact normally. However typing w gives this message

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING PARTITIONS!!

which suggests that data on the drive will be lost.

Is it possible to covert this disk back to GPT whilst keeping the data on it?

  • Even if you mess up terribly, there’s a very good chance. Knowing the original disk layout, you could try and find the beginning of the second partition manually using hexdump or the like.
    – Daniel B
    Aug 16, 2014 at 21:31
  • I would just convert it back; Why did you convert it knowing there was a MBR limit?
    – Ramhound
    Aug 16, 2014 at 23:34
  • I didn't know about the MBR limit at the time.
    – Joe
    Aug 18, 2014 at 7:39

1 Answer 1


First, take an image (yep, I know that you will need another 3TB disk, but it would be great, if you handle image, not the disk itself)

Many times I've recovered hard drives with "Active@ Partition Recover". No ads, it is really great software! Give a try.

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