Red Hat Enterprise Linux for Mainframe Computing is essentially the same operating system as SUSE Linux Enterprise Server for System z. But Novell generally gets mainframe hardware and software features into a release of SUSE Linux Enterprise Server (SLES) for System z a few months before they appear in Red Hat Enterprise Linux (RHEL) for Mainframe Computing. Novell has also developed a release cycle for distributed SLES that leads Red Hat's release cycle by about eight months. As a result, Novell typically has some features in its Linux distribution before Red Hat, and some of these features may beneficial to the mainframe. From a purely technical point of view, this gives SLES for System z a slim edge over RHEL for Mainframe Computing. From a subscription-cost point of view, there is little difference between the two distributions. Competition between Novell and Red Hat has taken subscription pricing out of decision-making.
Red Hat has made some strides in the Linux-for-mainframe market in recent years, which raises the question: Which of these two vendors should you select for your possible Linux-on-mainframe deployments?
SUSE had worked with IBM as early as 2000 (before Novell acquired SUSE in 2004) to develop a release of SUSE Linux for the mainframe. Shortly thereafter, IBM introduced the specialty engine Integrated Facility for Linux (IFL) to make running Linux-based software more economical. IBM says that approximately 4,600 IFLs were actively used in 2008. Over the past three years, the mainframe has become a cost-effective target for server virtualization, running migrated workloads on Linux virtual servers under z/VM, IBM's mainframe hypervisor operating system.
Prior to 2006, Novell had the Linux-for-mainframes market pretty much to itself, touting an 85% or higher market share. Red Hat was focused on the distributed Linux market and wasn't paying a lot of attention to Linux on the mainframe. After all, it was a less than a $20-million-per-year market for Linux subscriptions, and the selling cycle was long.
In 2004, Red Hat began paying some attention to Linux on System z servers, recording its first Red Hat Enterprise Linux for Mainframe Computing sale. Red Hat's subscription revenue for RHEL for mainframes was less than $1 million in 2004. In late 2005, Red Hat created dedicated System z sales, engineering and support teams. And in 2008, Red Hat's Linux-for-System z market share increased to 37% from 18.4% in 2007.
What made Red Hat change its mind about this seemingly small niche Linux market? It realized that there is drag-along revenue associated with each deployed RHEL operating system. For every dollar spent on Red Hat Enterprise Linux for Mainframe Computing, customers spend more than three times that for layered services such as middleware and consulting engagements.
When Red Hat began to show interest in the Linux-for-mainframe market in 2007, Novell countered by touting its eight- to 12-month lead time on new features.
Part of the reason Red Hat lagged Novell on Linux-for-mainframes was the Red Hat development model. Red Hat follows a development model called upstream development, meaning that Red Hat ensures that there is communal consensus about the technical implementation details of any given feature before it is released in RHEL. When a patch is committed that changes the way Linux talks to storage devices, for example, Red Hat makes sure that its x86 development team, its Power development team, etc. sign off on the feature.
At the time, SUSE, did not follow the upstream model for mainframe releases, so it was able to get new mainframe hardware and software features into SUSE Linux faster than Red Hat could get them into its distribution. It took Red Hat until late 2005 to begin to catch up with Novell. This is when Red Hat created its dedicated System z teams. Now the feature release delay between SLES for System z and RHEL for Mainframe Computing is about one to three months, with SUSE ahead. Red Hat says that Novell's claims about making mainframe features available well ahead of Red Hat is no longer a valid argument.
Red Hat has also taken another bold step to capture the Linux-for-mainframe market share lead from Novell by recently creating a Fedora for System z project. The development community for Linux for System z has always consisted of IBM, Novell and Red Hat. With Fedora for System z, the development community now includes anyone who wants to contribute. Today, Fedora for System z has a small but active development community. It allows developers to try out new features before they are integrated into RHEL. Red Hat claims that the Fedora for System z effort is helping to enhance its value proposition and take market share from Novell.
Selecting a Linux distribution for your mainframe
Let's come back to the question of how mainframe shops decide between Novell and Red Hat for their Linux-on-the-mainframe deployments. Red Hat dominates the distributed market, with Novell in second place, and Novell dominates the Linux-for-mainframe market, with Red Hat in second place. In both markets, the vendor that started first has the largest market share.
If you are contemplating Linux on the mainframe, take a look at what is running on your distributed Linux servers. If you are a distributed RHEL shop, or primarily a distributed RHEL shop, and you are happy with Red Hat's support, then RHEL is a good choice for your mainframes. We can say the same thing for SLES for System z if you are a Novell shop, or primarily a Novell shop.
If using the same vendor for both distributed and mainframe is not a requirement, I recommend that you talk with several mainframe customers that have experience with Linux for the mainframe running applications in production mode. If possible, speak with companies that have experience with both Linux-for-mainframe distributions. Some companies have done pilots with both RHEL and SLES on the mainframe, and a few companies have both Linux distributions running on the mainframe beyond pilot stage.
We have spoken to IBMers with extensive experience in Linux for the mainframe over the past few years as well as partners that sell both Novell and Red Hat. Most of them say they prefer SLES for System z versus RHEL for Mainframe Computing, but much of this view is a result of IBM's and its partners' long-standing relationships with Novell (initially SUSE), and Red Hat's failure to include new mainframe features in its distro as quickly as Novell. Red Hat's new interest in Linux for the mainframe may have them speaking a different tune now.
Today, Red Hat uses its huge installed base of distributed RHEL servers in data centers to leverage the sale of Red Hat Enterprise Linux for Mainframe Computing in data centers. Enterprise data centers that run Linux on the mainframe are very likely running SUSE Linux Enterprise Server for System z, and Novell is making the opposite argument to Red Hat's. Novell is trying to use its strong position in the Linux-for-mainframe market to get enterprises to replace RHEL on distributed servers with SLES or to choose SLES for new installations on distributed servers.
Application availability on Red Hat Enterprise Linux for Mainframe Computing and SUSE Linux Enterprise Server for System z could be important in making a choice. While both Novell and Red Hat have certified many of the same applications for their Linux distributions, both distributed and mainframe, you may have a set of applications that already run on one of the distributions and not on the other. This could be a deciding factor in making a choice.
ABOUT THE AUTHOR: Bill Claybrook is a marketing research analyst with over 30 years of experience in the computer industry, with the last 10 years in Linux and open source. From 1999 to 2004, Bill was Research Director, Linux and Open Source, at Aberdeen Group in Boston. He resigned his competitive analyst/Linux product marketing position at Novell in June 2009 after spending over four and a half years at the company. He is now President of New River Marketing Research in Concord, Mass. He holds a Ph.D. in Computer Science.
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This was first published in September 2009