Elgato Thunderbolt™ Dock supports booting from USB drives, in certain circumstances.
Computer Needed for Booting
For booting to work, the connected Mac must be "Late 2013" or later, with one of Intel's fourth-generation Core processors (also known as Haswell Macs).
OS Needed for Booting
For booting to work, the OS on the boot drive must be OS X 10.9.2 Mavericks, or later.
USB Version Needed for Booting
For booting to work, the drive can use either a USB 3.0 or 2.0 interface.
Partitioning Needed for Booting
For booting to work, GUID Partition Table (GPT) should be used for the drive.
Computer Needed for Booting
For booting to work, the connected Mac must be "Late 2013" or later, with one of Intel's fourth-generation Core processors (also known as Haswell Macs).
OS Needed for Booting
For booting to work, the OS on the boot drive must be OS X 10.9.2 Mavericks, or later.
USB Version Needed for Booting
For booting to work, the drive can use either a USB 3.0 or 2.0 interface.
Partitioning Needed for Booting
For booting to work, GUID Partition Table (GPT) should be used for the drive.