When you design a fault-tolerant system, your planning should definitely include uninterruptible power supplies (UPSs). 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 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:
The goal of any fault-tolerance measure is data availability. A UPS ensures access to the server if a power failure occurs—or 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 repaired.
In addition to keeping a server functioning long enough to safely shut it down, a UPS safeguards a server from inconsistent power. This inconsistent power can take many forms. A UPS protects a system from the following power-related threats:
A total failure of the power supplied to the server.
A short (usually less than 1 second) but intense increase in voltage. Spikes can do irreparable damage to any kind of equipment, especially computers.
Compared to a spike, a surge is a considerably longer (sometimes many seconds) but usually less intense increase in power. Surges can also damage your computer equipment.
A short-term voltage drop (the opposite of a spike). This type of voltage drop can cause a server to reboot.
A drop in voltage that usually lasts more than a few minutes.
Many of these power-related threats can occur without your knowledge; if you don’t have a UPS, you cannot prepare for them. For the cost, it is worth buying a UPS, if for no other reason than to sleep better at night.
Published on Tue 23 November 2004 by Dan Feathers in Networking with tag(s): ups