Open Source Success: Linux on the Mainframe

Twenty years ago, IBM opened its most proprietary computer technology—the data-centric, IBM Z mainframe platform—to Linux, an open source operating system. That decision may seem logical and straightforward given the now widespread adoption of Linux and open source software, but at the time it was a bold choice, and it has proven to be a resounding success. In this Resource article, we’ll look at this important link in the evolutionary chain of open source.

In Hindsight

In the announcement marking this 20-year anniversary of Linux on Z, Ross Mauri, General Manager for IBM Z, noted that “starting with Java in the late 1990s, IBM saw an opportunity to solve a major problem in the business world—bridging the gaps between existing technologies in their data centers and new business channels like the Internet.”

As Steven J. Vaughan-Nichols has reported, at that time, “Linux was the open source software darling and the IBM mainframe was the proprietary hardware king. IBM leadership could see, long before other major companies would, that Linux was the future of operating systems.”

Back in 2000, Vaughan-Nichols said, “Irving Wladawsky-Berger, then IBM's Vice President of Technology and Strategy, explained to the skeptical stockholders that ‘if Linux were just another operating system, we wouldn't be all that high on it. But that's what's so interesting. Linux is an operating system, but it's also radically different from anything that has come before it. It changes the way software is created and delivered.’”

Big Iron

Mainframes, or big iron, as they are sometimes called, have a reputation as monolithic workhorses, which is not necessarily wrong but is also an outdated view. Mainframes are really, really good at processing huge amounts of data, ensuring strong security, and offering fail-safe reliability. 

The technology has been around since the 1950s and has long been used in the financial sector, where these features are crucial; modern mainframes, however, are capable of much more. For example, the z15, which was released in 2019, is capable of handling 12 billion encrypted transactions a day and managing customer data across hybrid multi-cloud environments.

In this article, Javier Perez provided technical details of the underlying hardware and software that drives the IBM Z and LinuxONE mainframes: 

The processor architecture for IBM Z and LinuxONE is known as s390x. If you’re new to these two hardware platforms, they are commonly known as mainframes. IBM Z has had a tremendous evolution with world-class, enterprise-grade features for performance, security, reliability, and scale. The latest version, IBM z15, can co-locate different operating systems including Linux, z/OS, z/VSE, and z/TPF. The LinuxONE III model has the same features as IBM Z, but was designed exclusively for the Linux operating system, including most commercial and open source Linux distributions.


According to Philip MacLochlainn, an executive of IBM Systems Server, in this ZDNet article, "Early use cases were people running businesses, but also one of the first customers was NASA who used it to land on the moon." These days, the article stated, a “staggering amount of the world's commerce runs through IBM z.”

"It's pretty startling. 85% of all credit cards, 29 billion ATM transactions per year, 92 of the top 100 banks … 12 billion passenger flights are booked using IBM z each year, and if I trust Google and their count of the number of searches they do, we do 5x more transactions on mainframes—our customers do—than Google does searches each year," MacLochlainn said.

As Steven J. Vaughan-Nichols said, “Linux gave the mainframe new life. Instead of simply supporting old big iron jobs, the pairing of IBM and Z mainframes are finding new tasks for this powerful combination.” 

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