This hard disk from Verbatim is very good for the price ... but a little trick must be employed to use it to its full on modern operating systems. The problem Is that its SATA-USB bridge is configured by default to show the hard disk as two separate drives (not two partitions, two actual separate harddrives): one 2.2 TB, the other 800 GB. This is done to make the disk usable on older operating systems like Windows XP and, in principle, it is a wise approach ... if Verbatim so provided in the box some software to Easily change the configuration and have the hard drive shown as the 3TB disk it really is.
As a matter of fact, I could only find this software (as a Windows-only) on the Australian site of Verbatim. It would be really nice if Verbatim provided this software together with the disk and thus made a Mac version of it!
