Remote Control
Some PDUs provide remote access. Common methods include a RS-232 serial connection or a LAN network-controller accessible through Telnet, SSH, SNMP, or a web page. This allows an administrator to access the PDU from a remote terminal and interface with it to turn outlets on or off, to schedule power shutdowns, to control load, etc. This can be helpful if a remote machine has gone into an unresponsive state and will not restart through normal means. An administrator can connect to the PDU the machine is plugged into to power-cycle the machine.
One of the challenges in selecting PDUs for a data-center application is to balance the cost of the rack-PDU in the context of an organization's energy-management goals. Inexpensive rack-PDUs may distribute power effectively, but they offer little if any understanding or control of that energy flow. With energy costs rising over the past several years (circa 2010), IT professionals have begun to take a more comprehensive view of power management with rack-PDUs with more intelligence. The trend is more intelligence and higher-quality rack-PDU devices.
In North America the standard 240-volt circuit (120 volts x2 plus neutral and ground) has two legs at 120 volts. Most recently, data centers have begun to install single-phase 208-volt connections. Outside North America, the standard data center circuits are 230-volt AC and in higher end telecoms facilities 48V DC from giant UPS installations, neither of which are subdivided into other voltages by PDUs.
Read more about this topic: Power Distribution Unit
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