Institute for Advanced Professional Studies

2008 Server OS Reliability Survey*



The latest survey, which was completed in January 2008, served up some very interesting results and a few surprises. UNIX, the leading Linux distributions from Novell and Red Hat as well as open source Ubuntu were the clear winners in Yankee Group's 2007-2008 Global Server Operating Reliability Survey.

Yankee Group's second annual Server Operating System Reliability survey polled 700 users from 27 countries worldwide. The latest independent, non-sponsored Web-based survey revealed that all versions of UNIX -- which typically carry very high workloads -- are near bulletproof, achieving 99.999% reliability. IBM's AIX UNIX led all server operating systems for reliability with just over 30 minutes of per server annual downtime but Hewlett-Packard and Sun Microsystems also got high scores.

The top Linux distributions Red Hat Enterprise Linux (RHEL) and Novell SuSE Linux notched the biggest reliability improvements in the latest 2007-2008 survey. Each decreased per server per annum downtime by an average of 75%. The biggest and most unwelcome surprise in the survey was that Windows Server 2003 downtime increased by 25% to nearly 9 hours of per server, per year downtime compared to the results it achieved in Yankee Group's 2006 Global Server Reliability Survey. Windows Server 2003's decreased reliability is attributable to a series of security alerts Microsoft issued in the summer and fall time frame that caused network administrators to take their Windows Server 2003 machines offline for significantly longer periods of time to apply remedial patches.

In the past two years, the Yankee Group polls indicated that all of the major server operating system platforms have achieved a much higher degree of reliability than they experienced in the prior decade. In general, none of the major server operating systems -- Linux, Macintosh, Windows or UNIX are today beset by the long list of bugs that plagued their predecessors back in the 1980s and 1990s. Additionally, there is far less disparity now, in the number and severity of unplanned server outages and the time that businesses experience on their standard Linux, Windows and UNIX platforms, than at any time in recent memory.

Yankee Group's individual corporate Linux, Windows and UNIX servers experience an average of 1 to 4 failures, per server per year resulting in downtime that ranges from 1 hour to up to 10 hours of annual downtime for each server, depending on the server operating system and its specific configuration (See the graph of Hourly per Year Downtime per Server).

Among the other survey highlights:

  • UNIX-based servers, which represent about 10% of the installed base of server operating systems, achieved the highest reliability ratings among mainstream distributions.
  • IBM's AIX achieved the highest level of reliability with corporate enterprises reporting only 36 minutes of average per server downtime in a 12-month period. Hewlett-Packard's HP UX version 11.1 recorded 1.1 hours of downtime for each of its servers on a yearly basis, while Sun Microsystems' Solaris customers reported 1.4 hours of per server, per year downtime.
  • Both versions of Novell SuSE Linux -- the standard off the shelf distribution as well as the custom implementation -- saw downtime decline by 73% from just over 4 hours in Yankee's 2006 Global Server Reliability Survey to a little over 1 hour of per server annual downtime in the latest poll. The off-the-shelf version of Novell SuSE Linux, bested Red Hat reliability by recording 37 minutes less downtime for each server compared to the comparable off-the-shelf RHEL implementation. The customized version of SuSE Linux experienced 65 minutes of downtime per server, per year, roughly 13 minutes more for each server than its chief competitor RHEL in a custom configuration. Additionally, Novell's market share climbed from approximately 13% in last year's survey to roughly 17% in the current poll.
  • Linux market leader Red Hat scored similarly rosy results: per server downtime decreased by 75% for the standard off-the-shelf distribution to 1 3/4 hours for each server annually, down from just over 7.1 hours in Yankee Group's 2006 survey. Moreover, Red Hat's Enterprise Linux also increased in its enterprise presence. Custom implementations of RHEL delivered even greater reliability -- a scant 52 minutes of per server, per year of unplanned downtime. This year, 31% of the survey respondents reported they have standard RHEL present in their shops, up 5% from the 26% who had it installed in the 2006 survey.
  • Debian, a popular open source distribution, which last year posted the highest number of outage minutes, saw significant improvement in the latest 2007-2008 Global Server Reliability Survey. Debian servers this year experienced just over 5 hours of annual downtime a 41% decrease from the downtime figure it posted in Yankee Group's 2006 Global Server Reliability survey. And the open source operating system also increased its presence year-over-year with 24% of the respondents reporting they had at least one Debian server in their network compared to 15% who had it installed in the 2006 timeframe.
  • Ubuntu, which appears in Yankee Group's Global Reliability Survey for the first time this year, has also come on strong and is an open source operating system to be reckoned with. Some 22% of the survey respondents are running at least one Ubuntu server at their sites. And it has proven highly reliable, with 1.1 hour of per server, per annum downtime.

Disclaimer: Yankee Group polled over 700 users worldwide in this independent, non-vendor sponsored survey. Yankee Group also took precautions to ensure the integrity of the survey by implementing intrusion detection and authentication mechanisms to ensure that no parties could tamper with the results or vote more than once.

By Laura DiDio
Research Fellow, Enabling Technologies Enterprise, Software Economics and Infrastructure,
Yankee Group
Boston, MA

Posted: February 22, 2008

*Excerpts from a copyrighted newsletter prepared by the staff of WServerNews and distributed by IAPS with their permission. The views expressed in the above excerpts were drawn solely by WServerNews or Yankee Group and do not necessarily reflect the views of IAPS.



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