I have a 3TB USB3 drive that I want to use between my Mac and Windows laptops. A 1.5TB partition will be used for Time Machine and another 1.5TB partition will be used by Windows for file storage. The Windows partition will be ex-FAT because I want the files to be read/write able from both machines. The drive will be swapped between the two machines periodically.

On what OS should I create the two partitions so that it's usable by both OSes? I started by creating partitions in Windows. The Mac can see the Windows partition but when I try to format the parition for Time Machine, Disk Utility says:

Volume Erase failed with the error: MediaKit reports not enough space on device for requested operation.


  • I would strongly suggest partitioning the drive from your Mac. Most likely the partition you created in Windows is not in a format that Mac is expecting. – tubedogg Aug 24 '13 at 3:22
  • Learned that the hard way. I repartitioned on the Mac and now it works as expected on Mac and Windows. – Sajee Aug 30 '13 at 2:36

You must log in to answer this question.

Browse other questions tagged .