Promise Pegasus J2: superfast external mini-storage
 

The Promise Pegasus J2 can only carry 256 GB of data, but it is extremely fast, especially for an external hard disk. It is likely that the 512 GB version, which has two 256 GB disks, will perform even better. If you own a Thunderbolt-compatible computer and need fast external storage, then this Promise product is a great solution. And unlike its main competitor the LaCie Little Big Disk Thunderbolt, you can use it without plugging it into the wall, even if that does impact the performance.

http://uk.hardware.info/reviews/3537...l-mini-storage