I did some Thunderbolt Target Disk testing this weekend between two 2011 MacBook Pros with Apple (Toshiba) 3Gb/s SSDs (each capable of 200MB/s). Using both Finder Copy of a 1.2G file and QuickBench Extended test, the transfer rate averaged 62MB/s at best. Doing some digging, I learned that Target mode is very different from connecting to an external Thunderbolt drive. Target mode uses EFI. External Tbolt storage uses OS X. OS X can do multi-threaded, multi-block DMA transfers. EFI cant. It is 50% faster than FireWire 800 which measured 40MB/s in Target Disk mode. Thankfully, the external Thunderbolt RAID enclosures have been measured at speeds as high as 900MB/s. So a single external 6Gb/s SSD in a Thunderbolt enclosure should be able to achieve 500MB/s.