Uninterruptible Power Supply (UPS) for Lion Server
All networks should have an uninterruptible power supply (UPS) for the server and the OS X Lion Server is no exception. A UPS is an external box that keeps the server running in the event of a power failure in the building.
Some organizations need to keep the server running through the time of the power failure. A UPS also gives you a chance to shut down the server in an orderly fashion. Simply shutting off the power in the middle of operations can damage the data on the server, and power surges related to the power failure can damage the server hardware.
A basic UPS contains a backup battery and a surge protector. The server’s power cable plugs into the UPS and runs off battery power when the building power goes out.
More sophisticated UPS units include Automatic Voltage Regulation (AVR). AVR guarantees a constant level of power to the server in the event of fluctuations in delivered power, including short drops in power levels, or dips or surges that might occur before a total power outage.
One parameter to look at is the electrical load capacity, measured in volt-amps (VA). For a Mac mini or iMac, 350VA should do it. For a Mac Pro or Xserve, you can start at about 800VA. Extra drives and expansion cards draw more power and require a higher load capacity.
At the lower end, UPS boxes start at about $100 for a single outlet without AVR and can cost several hundred dollars for multiple outlets. Depending on the load capacity, a manufacturer will tell you how long the battery will run the computer — typically an hour or two at these price points, up to eight hours for units costing over $1,000.