Love and marriage may go together like a horse and carriage, but Linux and the IBM mainframe platform seemed until a year or so ago to be a rather more unlikely combination. The doyen of centralised computing running the darling of the Open Source community? Surely some mistake.
For IBM however, Linux running on the zSeries (or S/390) platform, helps it fulfil two major targets. It helps further the development of the open source operating system, which Big Blue has committed itself to spending $1bn to do; and it should help increase sales of what is still the company's flagship product, the mainframe, by making it more appealing to a wider audience.
So what exactly is so appealing about running Linux on the zSeries platform? 'Linux on the mainframe is principally a consolidation ploy,' said Richard Lechner, vice president of zSeries worldwide at IBM.
'I was at the Gartner Symposium recently, and a lot of the IT directors I spoke to there were very excited by server consolidation,' said Mike Lucas, technology director for Compuware. 'A lot of organisations end up with Linux being brought in at department level, and nobody admits to where it came from, but as these applications become more important the organisation has to put them somewhere.'
'We have over 500 customers who are piloting or in production with Linux on zSeries,' said Lechner. 'In addition we are seeing a substantial number of new customers who are buying the platform specifically because of Linux."
Since users can run multiple "virtual" instances of Linux on a single mainframe, it is possible to create literally thousands of virtual machines on the platform. IBM believes this fits in well with the second part of its strategy, with customers attracted by the appeal of being able to consolidate vast numbers of departmental servers running Linux on a single central platform
Users can also choose to run Linux as a native operating system on the S/390, by allocating it a logical - and physical - partition on the platform, but it is the virtual approach that is proving more popular Lechner claimed.
The latter approach uses IBM's VM (Virtual Machine) operating system, which allocates virtualised resources of processor and memory to each Linux instance. The Linux kernel treats these resources as physical hardware. For zVM IBM has changed the pricing to make it a one-time charge, so users do not have to pay more for large numbers of instances on a single machine.
"In fact this has caused a rebirth of VM," said Lechner. IBM is planning to bring the pricing of VM for its other servers in line with the zSeries, he said.
On the hardware side Linux will run on zSeries machines, as well as older models: the G5, the G6, and the Multiprise 3000. On the zSeries IBM has added high performance HiperSockets, which allow high-speed connectivity for TCP/IP traffic between partitions, which it claims can increase performance by up to 80 per cent. IBM has also enhanced integration between Linux and zOS.
IBM offers users the choice of Linux distribution from Red Hat, SuSe and TurboLinux. "We have no intention of going into the Linux distribution business ourselves," Lechner said. Nor will IBM support other players. "These companies are the largest Linux distributors so we see no reason to support others," he said.
Customer examples include Korean Airlines, which is consolidating its crew scheduling system off a number of NT servers to a single zSeries running Linux, and Reuters, which is posting its trading applications to Linux.
"People are always asking is Linux ready for prime time use, so this sort of move is very important for us," said Lechner. "There's nothing more mission critical than a trading application for a brokerage firm."
The ability to offer users access to their own virtual copies of Linux is also underpinning one of IBM's major development efforts, the Linux Community Development System (LCDS). Under this scheme, Linux developers can access Linux running on a mainframe via the internet, and use it to develop, port or test their own applications. For the developers this gives them access to the sort of hardware few could dream of affording, while IBM benefits by identifying Big Iron with the Open Source movement. Lechner said over 2,500 developers have so far taken advantage of the scheme.
If IBM is going to win customers to the platform today, however, then it needs applications to be available now, not sometime in the future. One of the first big commercial software vendors to offer support for Linux on the mainframe was enterprise resource planning software supplier SAP, which made its mySAP.com enterprise suite available for the platform earlier this year.
Other suppliers to support the platform include Computer Associates, Candle, and BEA Systems. Messaging software company SendMail is also a prominent supporter of Linux on the S/390, while other companies such as Oracle make a developer version of their products available for the platform. Siebel Systems is currently evaluating the platform.
But what's in it for IBM? Obvious benefits, apart from selling more servers, include services and support revenue for IBM Global Services, and increased sales of IBM's middleware products.
"IBM is investing significant money and pushing hard to make Linux work," said Meta Group analyst Dale Kutnick. "Traditional vendors like IBM, Intel and others will make money by using Linux to sell more hardware and services."
However, longer term IBM believes it will be in a good position through offering Linux on all its platforms. "Linux allows you to play in the space from the mainframe right down to pervasive devices," said Lechner.
"With IBM supporting Linux on all its platforms, it means you can write an application and run it anywhere," agreed Lucas.
IBM is also going back to school to capture support for Linux. "There are more people being trained on Linux in college than any other platform," said Lechner. This explains one of IBM's programmes of the last couple of years, namely its decision to provide universities with access to zSeries machines running Linux. The University of Warwick has benefited from this largesse.
In November, IBM extended its efforts to capture mindshare in the developer community by announcing it would make $40m worth of its software programming tools available to the public domain. The company also announced it would be one of the founder members of an organisation called Eclipse, along with Red Hat and SuSe, which would help to create Linux applications for e-business and Web services.
Overall, Lechner said he is confident of Linux's success on the S/390 platform. "IBM customers' use of Linux is growing at a triple-digit rate," he said. "In a tough economic environment that we have today things like cost of ownership, and better control of assets are at the top of peoples minds.