Some of those involved with the project had an ulterior motive. They knew that IBM’s Boëblingen, Germany team had started work on Linux for System/390, but internal politics blocked them from releasing it. Some Bigfoot team members wanted to force IBM to release their port, thus making it official. In January 2000, IBM released Linux for System/390. Although it was somewhat less than a commercial distribution — users had to download it from a site at Marist College — nevertheless it legitimized the concept and the Bigfoot project was quickly abandoned.
The revolution was quiet. No frontpage stories in Computerworld resulted (though some trade press did carry the story). Microsoft stock didn’t plunge. But within weeks, the System/390 port was downloaded hundreds of times and a vibrant Linux/390 community was growing.
Then, in February 2000, LinuxPlanet’s Scott Courtney wrote an article about an experiment in running multiple copies of Linux on one VM system. A consultant with access to a spare system spent a weekend building 41,000-odd Linux copies, each running an Apache Web server — and it worked! Admittedly, it was a stunt. The pages served were static, and the load was artificially generated and relatively minimal. But it proved the point. A single VM system could successfully replace multiple servers, using multiple copies of Linux.
Throughout 2000, IBM’s commitment to Linux grew. With the introduction of zSeries hardware in the fall of 2000, “Linux for System/390” became “Linux for System/390 and zSeries” — demonstrating that IBM had serious plans for Linux on the mainframe. In December, then-CEO Lou Gerstner announced that the company would spend $1 billion on Linux in 2001, and more in subsequent years.
Challenges and Opportunities
If the mainframe’s only payoff for Linux was yet another hardware platform, there would be little point in having done the port. Mainframe MIPS are far more expensive than Intel megahertz (MHz), so Linux on zSeries would just be an expensive solution to a problem nobody had posed.
Linux on VM’s real value lies in server consolidation — the ability to migrate dozens or hundreds of servers from distributed hardware to virtual machines running on a single z/VM system. A typical distributed environment includes spare machines for fail-over due to hardware or software problems, and “best practices” recommendations require planning for peak loads. The result is often tens or hundreds of machines running at less than 10 percent capacity, with attendant power, floorspace, cooling, networking, and administration requirements. With a single VM system, “spare” machines (extra Linux guests) require minimal additional resources. By sharing the system with multiple applications, all unlikely to peak simultaneously, you can safely over-commit hardware.
The combination of reduced Total Cost of Ownership (TCO) — attributable to savings on floorspace, cooling, networking, and administration — makes a compelling case for Linux on VM, even without considering Linux’s low acquisition costs. With the large number of tools and applications available for Linux, Linux under VM can replicate almost any distributed systems infrastructure.
The ability to easily clone an existing server for testing is also attractive. With deployment times for a new machine measured in seconds rather than days, developers and support staff can be much more responsive to problems. For example, if a Web-based application running on Apache on Linux has a problem, creating a “sandbox” for testing a fix is a matter of copying the existing server’s disks to a new virtual machine. If the underlying data is read-only, the process is even simpler. With no copying required, you can create a new virtual machine with links to the data. For companies with widely varied applications, this capability alone can justify exploring Linux on zSeries.
IBM quickly realized that, for Linux on zSeries to become the choice of CIOs, several hurdles needed to be overcome, including: