Drives larger than 2.2 TB may appear incorrectly when attached to an eSATA port
An eSATA drive larger than 2.2TB may appear to be smaller than it’s actual size when plugged in to an eSATA port. The disk may appear as the expected size if the drive is previously formatted using a different eSATA controller, USB, or 1394. In this scenario some read or write attempts may fail.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB981627.