How do you introduce a mainframe, a 40-year-old invention, to the world of modern IT? According to IBM, you run Linux on it. Big Blue says the open source OS, first offered on zSeries mainframes in 2000, now accounts for approximately 17 per cent of IBM's mainframe revenue and 22 per cent of hardware capacity shipped to customers. At the end of 2003, IBM had close to 300 customers running Linux in production environments and more than 1,000 customers in some stage of deployment.
Yes, you read that correctly. In an industry where many companies are pushing to replace mainframes with clusters of commodity Linux servers, IBM customers are spending big bucks to run the same OS on big iron.
To understand why, think in terms of total cost of ownership. According to Tim Kane, IBM's program director of Linux and virtualisation on zSeries, the management costs associated with clusters can quickly grow out of hand.
"It's easy to think of adding capacity in terms of, 'one more server, one more server,' " Kane says. "But over time, that adds up. If you add one per month, that's 12 servers by the end of the year. And many of our customers add more than one server per month."
The solution, Kane says, is to consolidate those distributed systems onto a single piece of hardware -- a zSeries mainframe -- using IBM's z/VM virtualisation software. Hundreds, even thousands of virtual Linux servers can run simultaneously on a single mainframe. The result is not just faster inter-application I/O but also a considerable reduction in the amount of space, electricity, manpower, and other resources needed to maintain the data centre.
"Very often, our strongest advocates are in the traditional IT organisation," Kane says. "They understand the value of the mainframe and some of the shortfalls of the three-tier distributed model."
Whether mainframe consolidation translates directly into reduced expenditures, however, is debatable. Hardware and software licensing costs keep mainframes mainly in the province of large corporations.
"Very few organisations that don't already have an IBM mainframe are likely to suddenly invest in the platform," says Mike Chuba, vice president and research director of storage and servers at Gartner. Chuba estimates IBM has added only about 100 first-time mainframe customers in each of the past two years. Still, some of those sales can be attributed to Linux for zSeries.
"While other platforms have narrowed the gap over the last five years, the IBM mainframe remains the gold standard, in many ways, for mission-critical workloads," Chuba says. "Note how many of the other server platforms now cite their 'mainframe attributes.' "
In other words: Why mimic the attributes of a mainframe with clustering when you can have the real thing?