How long does it take to boot? ie from power being applied through to it showing up as a target in other devices/apps. (The reason for asking is whether you n

How long does it take to boot? ie from power being applied through to it showing up as a target in other devices/apps. (The reason for asking is whether you need to connect it to a full time powered port, or one that only comes on once the TV etc are on. If it takes 5 minutes before becoming visible that would be problematic but 5 seconds would be fine.)