IBM's Power servers topped a list of most reliable x86 and Unix machines in a new survey, clocking in at only 15 minutes of unplanned downtime per year.
Linux distributions running on x86 servers also performed well, as did Sun's Sparc machines and HP's Unix boxes. Windows Server machines performed worse than most competitors, with two to three hours of downtime per year, but have still improved dramatically over previous surveys.
"Ten to 15 years ago, there was a lot more downtime [for all types of servers]," says Laura DiDio, lead analyst with Information Technology Intelligence. "Both the hardware and operating system software has gotten much better."
ITIC picked 15 of the most popular server hardware and operating system combinations, and polled C-level executives and IT managers at 400 organizations across 20 countries about unplanned downtime, patching, and other indicators of reliability.
IBM's Power servers with the AIX Unix operating system suffered an average of 15 minutes of unplanned downtime per year in the most recent survey, down from 30 minutes in the 2008 survey. IBM also came in first place for average time to patch a server (11 minutes per patch) and for lowest number of outages per year.
"For the second year in a row, IBM AIX Unix running on the Power or 'P' series servers, scored the highest reliability ratings among 15 different server operating system platforms -- including Linux, Mac OS X, Unix and Windows," DiDio writes in a blog post.
The second most reliable servers in terms of downtime were customized versions of Novell Suse Linux running on standard x86 hardware, clocking in at 17.4 minutes of downtime per year. Uncustomized Novell Suse Linux machines had 54 minutes of downtime.
Linux distributions such as TurboLinux and Mandriva on standard x86 hardware suffered 31.8 minutes of downtime a year, while Sun Solaris on Sparc servers suffered 35.4 minutes downtime a year.
HP 9000 servers running HP's Unix operating system came in fifth place with 36 minutes of downtime per year, while HP also took seventh place with Integrity servers (39 minutes downtime).
Apple's G4 Mac servers with the Mac OS X operating system came in sixth with 37.8 minutes downtime. "The survey respondents indicated that Apple products are extremely competitive in an enterprise setting," DiDio writes.
The worst performers were open source Linux distributions such as Debian, with more than four hours of unplanned downtime per year. The next worst were Windows Server 2003 on Intel-based hardware (three hours of downtime) and Windows Server 2008 (nearly two and a half hours downtime). But Windows Server systems also posted the biggest improvement, with a 35 percent reduction in downtime since 2008.
Ubuntu-based servers seemed to go backward, from one hour of downtime in 2008 to one hour, 41 minutes in 2009. That is more a function of the type of user attracted to Ubuntu, however, DiDio says.
"Ubuntu is very leading edge. Ubuntu users do a lot of experimentation" and can thus expect some downtime, she says.
DiDio attempted to measure reliability of most popular enterprise servers; she decided not to include mainframes, which probably would have taken the top spot.
"Mainframes are in a class by themselves," DiDio notes. "Whatever you say, you're not taking the mainframe down. It's like the Rock of Gibraltar."