I am unable to create an eDrive on my external drive.

There are two common reasons that TechTool Pro would be unable to create an eDrive on an external volume.

1. The volume structure is damaged.

Run the Volume Rebuild tool or Repair Disk in Disk Utility to repair the drive, and then try to create the eDrive again.

2. The external drive is not formatted correctly.

Ensure that the external drive is formatted GUID or Apple Partition Map.  To do this, open Disk Utility, and select the hardware name of the drive.  In the information at the bottom of the window, you should see the partition type.  If it says Master Boot Record, then you will need to reformat the drive as one of the above partition schemes in order to create the eDrive successfully.

Disk Utility

To re-partition a disk so that it is formatted correctly, you can do the following:

  1. With the device identifier selected, click the Partition Tab.
  2. Change the Partition Layout from Current to 1 Partition
  3. Click the Options... button, and change the partition scheme to GUID Partition table. Click OK.
  4. Ensure that Format: is Mac OS Extended (Journaled)
  5. Click Apply