The mainframe's virtual renaissance

When IBM first introduced the idea of a mainframe virtual machine back in the 1960s, few people would have predicted that the IT industry would have come full circle more than 40 years later. But increased interest in virtualisation and the demand for 'greener' computing could see a revival of interest in mainframe computing, according to some industry insiders.

"We are absolutely seeing interest in mainframes from clients who want to use more virtualisation," says Roy Illsley, a senior research analyst with Butler Group. "It's not an approach for everyone but, done well, it can reduce power consumption and footprint, improve reliability and provide a lot of value to the business."

Although virtualisation is most often discussed in terms of Wintel and Unix servers, the idea of consolidating many workloads onto a single machine and creating 'virtual partitions' was invented on the mainframe in 1967, says Carl Greiner, an analyst with Ovum. "This isn't a new idea by any stretch of the imagination, and virtualisation has always been done on mainframes."

The key advantage of using a mainframe for virtualisation is that it improves performance, says James Governor, a principal analyst with RedMonk. "Virtualisation technology on the mainframe is very mature, and offers availability, stability and security. For some applications and some customers, that's tremendously important."

Increasingly, companies are also coming around to the idea of mainframes offering better utilisation and efficiency, adds Illsley. "If you're looking to build a datacentre in London and you have the choice of consolidating onto 20 or 30 Wintel servers with the associated power and cooling bills — or a single mainframe that will use less power and reduce your footprint — well, it's quite compelling, for some companies," he says.

Today's mainframes can run thousands of virtual machines with very high utilisation rates, excellent security, downtime that's measured in minutes, and relatively low power consumption when measured as price per MIPS (millions of instructions per second).

Cost, flexibility and a fall from grace
So what led to the mainframe's decline almost 20 years ago, and are those issues still relevant today? Greiner argues that in the early 1990s, mainframes became very expensive for organisations to use for running new applications.

Mainframes have also suffered from a reputation for being inflexible; for example, applications cannot be easily converted to run on IBM's zOS mainframe operating system, so if the application has been written for another platfom it can often require a complete re-write to get it to work on zOS.

Many applications just aren't suited to a mainframe environment, Greiner adds. "If you're developing applications in .Net or Java, you're not going to be able to recompile them to run on a mainframe, and why would you want to?" he says. "Mainframes are for high transaction applications that require a lot of processing power, high availability or massive scalability."

Another reason for the mainframe's decline is a loss of skills in mainframe management. When organisations needed to cut IT spending in the 1990s, it was relatively easy to cut mainframe staff because the machines kept running with very little active management, says Illsley. "You ended up with these dusty, slightly forgotten machines in the back office that were just workhorses, and kept doing their job," he says.

A more open platform
To a certain extent, many of these issues have been addressed, say the experts. To begin with, IBM is now offering cheaper Linux engines at a fraction of the cost of conventional zOS engines, and the pricing model is no longer tied to MIPS, so users aren't paying for unused capacity, says Governor.

What's more, mainframe hardware and software have improved enormously in the past 20 years, so the platform is a good deal more open, says Governor. "IBM has made it a lot easier for companies to get data out of a mainframe and interrogate it using something like Websphere, as well as managing that data," he says. "Whereas once mainframes might have been seen as a bit of a roach motel for data, they're now a far more open platform."

So which companies are using mainframes in 2008? The vast majority of virtualisation on the mainframe happens when companies already have a mainframe and want to make it more valuable and efficient, says Greiner. "These are what I call mainframe-centric organisations and the chances are they are already virtualising on the mainframe, and are now turning their attention to using the platform to virtualise new applications or to enhance existing systems."

Many organisations would still consider a mainframe outside their budget, adds Greiner. "Although the price of a new mainframe has fallen, it's still probably only a handful of companies that are going out and buying the new machines specifically for this stuff," he says.

Governor agrees converts are most likely already using mainframes. He argues companies using mainframes today can be split into two camps. First, there are those who still love their mainframes, and are probably still looking to get the best performance from them — these companies...