Linux is a more efficient server operating system than Windows Server 2008 according to tests of three systems conducted by Network World.

The test compared Windows Server 2008, Red Hat's Enterprise Linux 5.1 and SUSE Enterprise Linux 10 SP1 running on Dell, IBM and HP servers.

In three of the 16 tests, Windows Server was the power efficiency leader, but only with maximum power settings turned on. Red Hat Linux used the least amount of energy in the remaining 13 test scenarios, using close to 10 percent less power than Windows Server in some.

The systems were put through two tests: one looked at how much power was used when each operating system and server pair sat idle for four hours in high power use mode and power savings mode; the other tested energy use when emails were continuously sent to each pair during the four hours in each mode.

The testers found that the main source of power savings for all systems came from mechanisms in CPUs that let the server slow down and rest when its not being heavily used, so its not running at the same pace and power all the time. However, two of the servers the systems were tested on had to be upgraded throughout the test period of maximize the efficiency of this "throttle back" mechanism.

"Tuning servers for optimized power savings could yield better results, but would create a new painstakingly tedious server management discipline required to constantly control the deep complexities of the configuration variables involved," the authors conclude. "We recommend that every potentially green server deployment be thoroughly checked, as each server model may or may not have the necessary BIOS settings and operating system chipset recognition features that will result in a power savings."