Linux drives a mainframe revival

Linux may not be everyone’s idea of a mainframe operating system, but for a growing number of large and medium-sized businesses the synergy between Linux and big iron is the solution to a significant problem.

Linux may not be everyone’s idea of a mainframe operating system, but for a growing number of large and medium-sized businesses the synergy between Linux and big iron is the solution to a significant problem.

Many users want to consolidate their burgeoning populations of distributed Linux applications and to find a way of applying centralised management and security. And when it comes to consolidation, the System z takes some beating.

IBM mainframe support was a late addition to the Linux repertoire. Work on the project began around 1997 and Linux/390 (the predecessor to zLinux) was rolled out in 1999, some eight years after Linus Torvalds first unveiled his software.

But it was 2001 before the real value of the Linux/mainframe combination became clear. That is when the Integrated Facility for Linux (IFL) became available – the first of several “specialty engines” that IBM has rolled out to make new workloads much cheaper and easier to support on the mainframe than legacy applications.

The other development that made Linux popular on the mainframe was the re-emergence of VM, IBM’s venerable hypervisor, which has proved immensely scalable as a consolidation environment for multiple Linux images.

According to one research source, more than 40% of IBM’s System z customers (who include most of the world’s largest banks, insurance companies, retailers and utilities) are now running the open source software on the mainframe, whether it be in a mission-critical role, as a consolidation solution, or on a trial basis.

And it is not just users that are showing growing enthusiasm for centralised Linux servers. Oracle and IBM have joined forces to market a range of business solutions based on Oracle Applications running on Linux on System z. A similar agreement was recently forged between IBM and SAP, and it is clear that the industry’s strategic application providers see an attractive top-end market developing for their products.

So what does the mainframe offer that other platforms don’t?

Scalability is certainly one factor. VM allows the user to support hundreds (technically thousands) of Linux images on one system, and to set up new ones within minutes. One US company, for example, reported that it had consolidated 350 distributed servers onto 15 engines within its mainframe configuration, and this is by no means exceptional.

Linux consolidation is not only a cost issue: it allows businesses to rationalise their datacentre resources logically. The System z runs at anything up to 100% utilisation (compared with maybe 50% for Unix servers and often single digits for PCs), and consolidation can bring big savings in floor space and power consumption – issues that are more significant today than ever before.

Security is another of the mainframe’s big advantages, and the tools that control access on the System z (RACF, ACF2, Top Secret) have reached a level of maturity that is rarely reflected on other platforms. With current legal and political concerns about privacy and data integrity, there are benefits in managing security in one centralised location.

For users who already have a significant investment in mainframe applications, there are strong arguments for running Linux applications as close as possible to the host software, maybe in a neighbouring logical partition. This allows data to be shared securely and at extremely high levels of performance, without the inefficiencies of sharing resources across a distributed network.

This is all fine for existing mainframe users, who know the technology, have the skills in place, and maybe have spare capacity available to dedicate to Linux applications. The mainframe remains a difficult sale, though, among users who do not have a System z background, or who require buy-in from a board of directors who think the mainframe went out with the Ark.

Even in sites where the mainframe is well established, there is often resistance to consolidation among those who “own” the distributed servers and fear losing them to the clutches of the mainframe datacentre.

These are not easy obstacles to overcome, but with IBM’s continuing efforts to bring down the price of “new application” capacity on the mainframe, more support from the major application suppliers, and regulatory pressure on users to manage their distributed servers more efficiently, the mainframe may be coming back into fashion.

Mark Lillycrop is managing director of Arcati, a consultancy that provides financial and technical information for mainframe users


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