As I already indicated in an emailed response, a LaCie or WD USB3 or Thunderbolt drive should work fine and will boot.
Note that some Macs don't like booting with some USB3 drives if they're in "SuperSpeed" mode (that is, using a USB3 cable). Substituting a USB2 cable (which will fit in 1/2 the port) at boot time will resolve that.
__________________
--Dave Nanian
|