Working with Uninterruptible Power Supplies
One other fault-tolerance strategy that we should take a look at involves the use of an uninterruptible power supply (UPS) . A UPS is a device outfitted with some type of battery that can supply temporary power to a server when there is a power failure. Many UPS devices will also offer surge protection; this will help protect an important device from any voltage surges that may occur during an electrical storm or other power surge problem.
A UPS sits between a server and an electrical outlet. The UPS is plugged into the electrical outlet, and the server is plugged into the UPS. Because the UPS is a peripheral device, it also connects to the computer via a serial cable or a UPS port. The serial cable used is not your typical serial communications cable and will be included with the UPS.
UPS devices also come with their own software that needs to be installed or configured with the appropriate drivers offered by the operating system you are using. This way, they can relay alerts to the operating system related to electrical spikes and brownouts.
A UPS really serves as a silent partner to the server until there is an electrical problem. When power from the outlet is available, the server will be powered by that electricity. At the same time, the UPS is charging its battery.
If the electricity goes out, the UPS will step in and power the server using its battery. This typically supplies the server with 5 to 30 minutes of power. This basically gives you, the network administrator, time to shut down the server properly so that there is no data lost.
It makes sense to use a UPS on servers because most network operating systems can become corrupt or experience problems when they power up again if they have not been shut down correctly. How sophisticated the UPS devices should be on your network (in terms of the alerts they can supply and the amount of battery power they can supply) will depend on how quickly you can get to the servers and actually shut them down. Some UPS devices can even be outfitted with a modem and can be configured to call your pager when there is an electrical problem.
You can also use a UPS to protect other mission-critical failure points on your network. A UPS can be attached to switches, routers, hubs, or any other device that you wish to keep up and running for a short period of time when there is a power failure.