uninterruptible power supply (UPS) A device that can temporarily provide power to network components. Overview Downtime of computer networks and systems are the bane of today.s 24x7 e-businesses, so guarding against such a condition is essential to the enterprise network architect. One of the key weapons in an administrator.s arsenal is the uninterruptible power supply (UPS), which provides: . Temporary power against brief power outages to prevent mission-critical data from being lost and against extended power failures to enable servers and other key networking components to be shut down in an orderly manner . Power conditioning to eliminate harmful surges and brownouts that can corrupt data and damage equipment The standard UPS is typically a device with rechargeable batteries and software drivers that can perform operations such as: . Notifying users that a shutdown is imminent and that they should save their work . Pausing services on servers to prevent new connections from being established . Providing enough power to perform a soft shutdown of servers and other key network components . Performing other actions as specified in a batch file that runs automatically . Providing power line conditioning and smoothing out spikes and dips in the power flow UPS devices range from small stand-alone boxes to rack-mountable units to room-sized devices having integrated diesel generators for extended power generation. UPS devices are generally rated according to two values: . Volt-amp (VA) or kilovolt-amp (kVA) rating: This determines how much connected computer and networking equipment the UPS is capable of supporting. The larger the VA or kVA value, the greater the number and higher the power requirements of connected devices it can support. UPS devices range from small 1000 VA (1 kVA) units costing $100 or so and designed for Small Office/ Home Office (SOHO) computer networks and servers to huge high-end 500-kVA units costing thousands of dollars and designed for mission-critical needs such as those of banks and hospitals. Note that UPS devices can also be rated in watts (W) since 1 VA is equal to 1 W and 1 kVA equals 1 kilowatt (kW), but for some reason general usage is to rate them in VA and kVA instead. . Time@100%(min): This is the amount of time that the unit can sustain maximum power generation. Small and mid-sized UPS devices can typically provide 100 percent power to network components and computers for between 5 and 15 minutes after a power failure. You can use additional battery packs with some UPS devices to extend uptime further. Marketplace Some of the larger vendors of UPS devices include American Power Conversion Corporation, Best Power, Clary Corporation, Exide Technologies, Falcon Electric, Liebert Corporation, ONEAC Corporation, OPTIUPS, Powerware, Toshiba Corporation, Tripp Lite, and Tsi Power Corporation. An example of a high-end UPS is the Silcon DP300E from American Power Conversion, which comes in various models rated up to 1.6 megawatts (MW). Such high-end UPS devices are designed for the largest data centers. Notes Always test your UPS after installing it. Otherwise, you might be sorry when a power failure happens in your neighborhood! A good way of testing a UPS is simply to unplug a computer on your system and watch what happens. Some UPS units support Simple Network Management Protocol (SNMP), which lets you test the condition of the UPS at regular intervals and report the results to an SNMP management console. Note also that the larger the load attached to a UPS unit, the shorter the time interval the unit can continue powering attached devices during a power outage. Be sure that your UPS unit can support your power needs for the time needed to properly shut down your system. To determine what size UPS you need for your network, add the wattages of all the devices you want to connect and ensure that you buy a UPS unit whose VA rating exceeds this value by a good margin.