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ITGlossary · UPS technology
Redundancy
Having more UPS units or modules than the load needs, typically in an N+1 or 2N configuration, so the load stays powered if one fails.
Technical level:Intermediate
To keep a critical system running when a component fails, more units are installed than the load actually requires. The most common UPS arrangement is N+1: if the load needs two units, three are installed in parallel, so that if one goes out of service the others carry on. More demanding data centres use a 2N arrangement, with two fully independent power paths.
Redundancy increases availability and allows maintenance without interrupting the load, but it adds cost and takes up more space. Modular UPS systems make it more affordable, since a single extra power module is enough.
A common mistake: an N+1 system stops being redundant once the load grows and needs every unit. Check the load periodically.
Related articles
Related terms
- Modular UPSA UPS design where independent modules can be combined to meet power and redundancy needs.
- Six Nines AvailabilityAvailability of 99.9999%, about 32 seconds of downtime a year, which requires redundancy across the whole power chain.
- Capacity SystemParallel UPS units that share the load with no spare unit (N configuration), so the failure of one unit overloads the rest.
- Redundant Power SupplyA second power supply inside a server or switch that takes over without interruption if the first one fails or loses its feed.
- Double Conversion EfficiencyThe share of input power that an online UPS delivers to its output, lower at light load and highest at medium to high load.
- Maintenance BypassA manual switch used to isolate the UPS for servicing while still supplying power to the load.