On an unmanaged dedicated server or VDS, many customers have run DayZ servers successfully. Installing and maintaining a DayZ server requires contacting the developer of the game and coordinating with them to obtain its files and add it to their whitelisting system, as well as the adoption of certain rules and practices when it comes to server administration.
On a managed dedicated server, managed VDS, or our shared hosting, it is not currently possible to run DayZ. This is because DayZ requires a constantly-updated ArmA2:OA beta installation, including the beta .exe. Our system locks, renames, and maintains the integrity of all .exe files, which means that we would have to support and track the latest beta throughout our system, which is not feasible at the present time.
We sincerely hope that a stable ArmA2:OA official non-beta version is released soon, and that DayZ also stabilizes (as of this writing, it is still in an "alpha" phase).