How much space is required for the eDrive partition on my hard drive?
The eDrive partition will be 4 GB to 6 GB in size, depending on the version of Mac OS X on the eDrive and the version of TechTool Pro 4 used to create it. Be sure there is enough free space remaining on the volume from which the eDrive is created, so that the original volume will have at least 10% to 15% free space remaining after creating the eDrive.