1. The first recommended medium is Standard Image File device, because it supports unlimited capacity, and easy to be migrated, backup, expended and even we support continues data protection (snapshot) for this medium.
2. The second recommended medium is Virtual Hard File device, except the capacity limitation (2040 GB), it is all the same as the Standard Image File.
3. If you really want to use a physical device, it is also supported, just like physical disk, partition disk, and General SCSI device, but be sure you have choose the option “Persistent Exclusive Access on this device”.