The mainframe's virtual renaissance

• Tags:
• Server,
• Consolidation,
• Mainframe

Sally Whittle ZDNet.co.uk

Published: 02 Jun 2008 13:16 BST

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...will be actively investigating virtualisation. Second, there are mainframe owners who haven't updated their systems in some time, and have basically left the machines to their own devices for many years, running important back-office applications. These companies are unlikely to have explored virtualisation and may never do so, says Governor.

The risk is that companies falling into the second group will try and deploy virtualisation on the mainframe without first modernising and rationalising their IT environment — and in so doing, fail to fully realise the benefits of the technology. Simply taking existing applications and moving them wholesale onto a mainframe to improve utilisation is "madness", says Governor. "It makes no sense at all, you don't get any business benefit and no cost benefit either," he says.

Reaping the potential benefits
To achieve the benefits of mainframe virtualisation, the first step is rationalisation.

This starts with a thorough audit of the IT environment, says Paul Hammond, UK managing director of consulting firm Glasshouse. It involves calculating and checking all existing systems: everything from current rack space and power consumption to which applications run on which servers should be included. "We often find companies where there are three or four finance systems being used, when it would be easier to use one or two," says Hammond. "It's important to identify those sorts of issues before doing any virtualisation."

Next, companies should carefully assess what physical servers are running what operating systems and applications, and conducting a consolidation programme. Do you need all your current applications? Are some applications more suitable for running in a mainframe environment?

As part of this analysis, Greiner advises businesses to consider carefully the costs of virtualising, including any recompiling or rewriting of applications that might be needed when running applications in a virtualised mainframe. "If you have a pile of Linux applications running on Wintel servers with 10 percent utilisation, then virtualisation and porting them to a mainframe won't be a problem, but with certain applications, such as those written in Java or .Net, it might be possible to get them running in a mainframe given the right engine and tools, but it's unlikely to be cost-effective or even particularly necessary."

So will the cost of recompiling an application for the mainframe outweigh the expected performance benefits? Would it be better to simply virtualise on a Wintel or Unix server, or perhaps invest in a new Linux application that can more easily be ported to the mainframe?

Some applications are inherently more suitable to run in a mainframe environment, and obvious advice is simply to focus on moving those applications back into a virtualised mainframe environment, says Greiner. "It makes no sense to go and compartmentalise your new SOA architecture and move it onto a mainframe, but if you have high transaction applications that demand reliability and availability, this may be a viable alternative," he says.

For example, database applications often struggle in a virtualised environment of any kind, says Illsley. "Virtualising doesn't guarantee better performance — you have to do the right virtualisation for your workload," he says.

'Fool with a tool'
It's often hard work to convince clients virtualisation is not a solution in itself, says Hammond. "There's no point in transferring all your bad practice to a new and expensive platform," he says. "We urge clients to spend a lot of time thinking about where they can consolidate applications, how their data-management policies can be improved, and work on robust service cost models that show businesses the cost and benefits of running specific services in a virtualised mainframe environment."

The reality is that even moving bad data and practices onto a mainframe will generate some benefits in performance and utilisation — but these will be far greater if you do the upfront work, or at least do this work on an ongoing basis once the migration is complete. "We call virtualisation a fool with a tool," says Illsley. "If you throw stuff onto a mainframe without thinking about it, you'll probably improve virtualisation by default, but you'll never get the performance or efficiency that justifies the cost of the platform."

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