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Old, not obsolete: IBM takes Linux mainframes back to the future

Your KVMs, give them to me

IBM introduced several significant new elements for its Linux server stack last month: support for KVM on its z Systems mainframes, Linux-only models in both the z Systems and Power Systems ranges, and a new purchasing model.

The most technically interesting new development is mainframe support for KVM, the Linux kernel’s built-in hypervisor. Although this is just a new way to access facilities that existing IBM products offer, it may help drive migration of x86 workloads onto IBM’s highest-end kit.

Big Blue’s big iron already has rich virtualisation offerings. At the lowest level, the PR/SM facility splits each machine’s resources into multiple logical partitions (LPARs), each appearing as a separate machine with a portion of the host’s processing and storage capacity. Even if the machine’s configured as a single unit, it’s really one LPAR.

Inside an LPAR, you can run a mainframe OS, such as z/OS or IBM’s “virtual machine OS”, z/VM. (IBM’s virtualisation technology dates back to 1972 and thus predates VMware and its ilk by decades – meaning that IBM uses different terminology. In PC parlance, z/VM is a type 1 hypervisor.) Inside z/VM, you can run other mainframe OSs, including multiple copies of Linux.

The snag is that if you’re coming across from the PC world, z/VM is significantly different from anything you’re used to, based as it is on over 40 years of mainframe tradition. One way to avoid that is to run the Linux kernel straight on the metal of your LPAR, but that significantly reduces the number of instances you can run and the flexibility of managing them.

KVM for Linux resolves this – instead of a daunting mainframe OS, you can use existing techniques to run Linux VMs under Linux itself.

And since Linux on z Systems is just Linux, this also applies to management and orchestration tools, too, including anything written in any scripting language supported on the mainframe distros: Red Hat Enterprise Linux, SUSE Linux Enterprise and most recently Ubuntu.

Keeping up the Linux push are the new z13 mainframes. The LinuxONE range currently comprises two Linux-only models: the mid-range Rockhopper and the high-end Emperor. There isn’t really such a thing as an entry-level mainframe.

Also, note the penguin-themed names – this sort of playfulness was very much not the style of the IBM of old. The Emperor model can scale up to 10TB of memory and 8,000 VMs.

Meanwhile, over in the world of slightly more commodity kit ... although Lenovo finalised the purchase of IBM’s x86 server range back in January, Big Blue does still have its own RISC processor line – the POWER series.

This CPU family is most famous as the basis for the PowerPC chips that used to power Apple’s Power Macintosh and the xBox 360, but the original high-end line is very much alive.

The latest iteration is POWER8, and it includes the other interesting technical development. There’s all the usual “bigger, better, faster more” stuff that accompanies the launch of any new processor family – such as the news that version 8 of POWER supports up to eight hardware threads per core, compared with Intel which can only manage two.

The bigger news, if you know anything about CPU architectures, is bi-endian operation. Previous generations of POWER processors supported handling x86-style little-endian data, but code had to be big-endian.

Version 8 supports completely little-endian operation, meaning that x86 code can now be ported with a simple recompile. This should make it a more attractive proposition to the vast majority of server users who run plain old PC kit.

Hoping to cash in on this, IBM is now offering Power Systems boxes that only run Linux – a surprising move given that it has two OSs of its own for its other Power-based machines: IBM’s Unix, AIX, and IBM System i, the old OS/400.

Plus, in the fairly unlikely event that you’ve got old big-endian POWER code or workloads, the Power Systems’ built-in PowerVM hypervisor can run both types of distro side-by-side on the same machine – and they support KVM, too.

IBM introduced two new machines: the S812LC and the S822LC.

The S812 can take either a 3.32GHz 8-core CPU or a 2.92GHz 10-core one, up to a terabyte of RAM and 14 LFF (so, 3.5 inch) drive bays. The S822 doesn’t have all the drive bays – just a pair of SFF (2.5 inch) bays – but it supports two processor cards and optional nVidia Tesla GPUs for GPGPU workloads.

The POWER8 processors look to be competitive with Intel chips in performance terms and porting x86 Linux code to them is easier than for any previous generation of POWER-based machines.

Support for KVM virtualisation on both Power Systems and z Systems – including cheaper models that can run only Linux, not any of IBM’s proprietary OSs – should ease integration pains and mean that tooling can be brought straight across.

How do you obtain one of these machines? The new RISC servers can be bought direct, online, from the company. Indeed, IBM’s product page sports “IBM Web prices”.

At time of writing, this wasn’t available in all countries yet, but it’s an important step for the 104-year-old company. IBM is trying to prove that it is, to quote the most recent Terminator movie, “Old, not obsolete.”

A bit like a wrinkly grey-haired T-800, you find yourself rooting for it. ®

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