The server tests rated power consumption on IBM, Dell and HP machines in three conditions: active mode optimized for power savings, active mode optimized for performance and quiet mode.
RHEL 5 had the single widest lead, with 12% greater efficiency than Windows Server 2008 on IBM x3350. Results varied by hardware, but RHEL had the best overall performance in 13 of 16 tests and, in several trials, beat Windows by nearly 10% .
"It's always nice to do well," said Red Hat Marketing Manager Nick Carr. "But I'd expect a certain amount of leapfrogging. That's the nature of rapid development."
The independent testers agreed that the energy lead is likely to toggle back and forth among the different operating systems as they become more finely tuned to the latest chipsets.Working together to reduce power draw
Hardware and software vendors alike have worked to improve power management, hardware vendors through the BIOS, and operating system vendors through intelligent regulation of CPUs and memory, Carr said. Red Hat's 80% market share of the Linux market gives it an edge in working with hardware vendors to optimize their chipsets to work with the latest operating system improvements, he added.
Open source vendors have an inherent advantage over proprietary OS vendors like Microsoft because they have collaborated with the community to leverage new features, incorporating one another's improvements and bringing innovation to market faster, Carr said.
One example of open source collaboration is the LessWatts organization, which draws expertise from Intel and other hardware vendors to optimize chipsets for power management, he said. The Intel-led community initiative developed energy-saving innovations such as Tickless Idle, which reduces power by eliminating unnecessary processor activity when the computer is not working, and PowerTop, a test that identifies sources of power inefficiency in hardware and software applications and offers tuning suggestions.
Red Hat's recent power test victory came before it incorporated Tickless Idle into its operating system, which should boost energy efficiency further. Tickless Idle has been added into Fedora, Red Hat's free, community operating system but won't be added to the platform until the release of Red Hat Enterprise Linux 6 sometime in the future, Cathrow said. Novell, also must wait until the next major release of SUSE Linux Enterprise to add Tickless Idle.
Another challenge with optimizing servers for energy efficiency is the difficulty of the optimization task itself, the test report noted. However, Red Hat has best practice reference materials to help customers with this task, Cathrow said. In addition, Red Hat is working to simplify system adjustments for power or performance by adding seamless interfaces between firmware and the chipset so the operating system has to be adjusted only once, Cathrow said.
Ultimately, there is some question whether users will take advantage of an operating system's energy-saving features, as some of these measures exact a cost in performance and response time of the system. This confronts systems administrators with a choice of tuning machines to maximize one or the other.
"You don't want to run down the clock rate," said Andy Cathrow, Red Hat marketing manager, referring to the speed with which computers perform basic operations. "You have to have the right balance."