Hands on: Linux beats Windows Server 2008 power-saving measures

Network World - Ensuring that your servers stamp as small a carbon footprint as possible on the earth and in your data center can encompass everything from making sure they are shipped in recyclable packaging to hiring an analyst who can predict the total life-cycle environmental impact.

For this test, we examined power consumption as a way to judge whether Windows Server 2008 or Linux is, in fact, the "greener" operating system. As the price of power hits record heights, power-reduction mechanisms shipping within an operating system should play a key role in your energy conservation plan.

Our tests point to Linux as the winner of the green flag by margins that topped out at 12%. But we must note that our results are full of stipulations imposed by our test bed, and as the more truthful car advertisements might warn, your wattage may vary.

We ran multiple power-consumption tests using Windows Server 2008 Enterprise Edition, Red Hat Enterprise Linux (RHEL) 5.1 and SUSE Enterprise Linux 10 SP1 on four popular 1U server machines (1U is 1.75 in. high). These included one each from Dell and IBM and two from Hewlett-Packard.

The results showed that while Windows Server 2008 drew slightly less power in a few test cases when it had its maximum power-saving settings turned on, it was RHEL that did the best job of keeping the power draw in check across the board.

The variable settings allowed by both Windows and Linux -- which let you toggle between having a highly energy-efficient server vs. a high-performing one -- can certainly have an impact on overall server consumption. But again, your mileage will vary given the workloads you place on your servers and whether or not you're using popular virtual machine hypervisors to support multiple operating system instances on the same physical server. (See related story.)

The edge in either test category will likely not last as operating systems become more finely tuned to work in lockstep with advanced server chip sets and as additional coding techniques that more closely tie operating systems and applications to power considerations take hold across the industry.

Part of the current "green" operating system difficulty lies in the disconnect between how an operating system and applications can be optimized to let the underlying system move to a state that consumes less power while at the same time not sacrificing the ability to react to application (and therefore system and user) needs.

In our testing, we found that the CPU "throttle-back" mechanism -- the main technique for an operating system to help reduce a server's energy draw -- requires new firmware and updated drivers that specifically support that feature. Only the IBM x3550 and the HP DL-360 G5 arrived ready for optimal power conservation. The HP DL-160 and Dell 1950 servers required several updates throughout our six-week test period to accommodate the CPU throttling features of Windows 2008 and Linux.