Using Uninterruptible Power Supplies

No discussion of fault tolerance can be complete without a look at power-related issues and the mechanisms used to combat them. When you're designing a fault-tolerant system, your planning should definitely include UPSs (Uninterruptible Power Supplies). A UPS serves many functions and is a major part of server consideration and implementation.

On a basic level, a UPS is a box that holds a battery and a built-in charging circuit. During times of good power, the battery is recharged; when the UPS is needed, it's ready to provide power to the server. Most often, the UPS is required to provide enough power to give the administrator time to shut down the server in an orderly fashion, preventing any potential data loss from a dirty shutdown.

Why Use a UPS?

Organizations of all shapes and sizes need UPSs as part of their fault-tolerance strategies. A UPS is as important as any other fault-tolerance measure. Three key reasons make a UPS necessary:

  • Data availability The goal of any fault-tolerance measure is data availability. A UPS ensures access to the server in the event of a power failureor at least as long as it takes to save a file.

  • Protection from data loss Fluctuations in power or a sudden power down can damage the data on the server system. In addition, many servers take full advantage of caching, and a sudden loss of power could cause the loss of all information held in cache.

  • Protection from hardware damage Constant power fluctuations or sudden power downs can damage hardware components within a computer. Damaged hardware can lead to reduced data availability while the hardware is being repaired.