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Linux update on IBM System p

Most machines running Linux are x86 PCs. IBM's System p and Linux go well together, and Ken Milberg explains why and what's new. He gives five reasons to run Linux on System p, and shares some of the options for PowerVM, IBM's virtualization platform.

Without question – the vast majority of Linux users run Linux on x86 PCs. What is it about Linux on IBM's System p that sets it apart from other platforms? What recent enhancements have been made to Linux on IBM's midrange architecture? These are some of the topics we'll tackle in this article on Linux on Power (LoP).

I'll start with a short introduction for those of you that have not heard of this platform. The IBM System p is IBM's midrange architecture, formerly referred to as RS6000's. The company's midrange architecture has come a long way since the days when you could only run one operating system on one physical box, sans virtualization, and the OS was limited to IBM's AIX. Today, using IBM's virtualization technology, PowerVM and its logical partitioning (LPAR) hypervisor based technology, not only can you run multiple operating system instances on one physical server, you can run both Unix (IBM's AIX ) and Linux (SLES & RHEL). RHEL4, 5 and SLES9 and 10 are supported.

Why run Linux on a System p?
There are really five reasons:

  1. Scalability – The top-of-the-line IBM System p 595, powered by the fastest processor out there (the 5.0GHz POWER6) processor, can be equipped with up to 64 processors. Using IBM's Virtualization solution, PowerVM you can have up to 640 logical partitions, as each partition can have up to 1/10 of a CPU.
  2. RAS functionality – When you look at a high-end IBM System p, you may think it's a mainframe. That's because the high-end systems have the mainframe chassis and mainframe-type reliability. RAS features built into the System p for Linux include predictive failure analysis and diagnostics, robust journaled file systems including ext3 and ReiserFS, fault tolerance with redundant power and cooling and automatic first-failure data capture. What is more impressive is that you no longer need to run AIX to get the full RAS benefits of the hardware.
  3. Consolidation – Using PowerVM, enterprise users can now consolidate servers much more efficiently. Unlike other hardware platforms, the IBM System p allows you to share both CPU and I/O resources. For example, QA and development environments that may not require dedicated network interface cards (NICs) can now share NICs using the Virtual I/O (VIOS) capabilities of the System p.
  4. Performance. – Raw performance is what the System p offers. In recent benchmarks, the 64-core IBM Power 595 server outperformed the 128-core HP Integrity Superdome, which has twice the amount of cores. The 595 also has 90% of the performance of the 256 Sun SPARC Enterprise M9000 – 90% of the performance with only one-quarter of the cores.
  5. Manageability and support – More than any other benefit, IBM support means that corporate folks can get over their fear of a move to Linux because they will be getting the same world-class support they have always had on other IBM supported operating systems, such as AIX.

What's new?
During the past year IBM's virtualization engine on the midrange, Advanced Power Virtualization (APV), has been rebranded to PowerVM. There are now three types of virtualization packages available on Linux: PowerVMExpress Edition, PowerVM Standard Edition, and PowerVM EnterpriseEdition3. All of these support Micro-Partitioning and IBM's VIO server – albeit to varying degrees. Micro-partitioning refers to the ability to divide physical processors and share them among multiple logical partitions.

What's the difference between the products?

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PowerVM Express supports up to three LPARs (one of which must be a Virtual I/O partition) per server and is meant for very small boxes (520 and 550 models). You can't use a Hardware Management Console (HMC) with the Express version and you also can't take advantage of several new Power6 innovations, such as multiple shared processor pools or live partition mobility.

PowerVM Standard supports up 10 LPARs per core. In other words you can carve up a single CPU to run one-tenth of a CPU per host. You can use the HMC for the Standard edition. Supported platforms include; POWER5, POWER6, JS21, JS22. The other feature available on Standard and not the Express edition is the multiple shared processor pool feature. What are these pools? LPARS typically have multiple LPARs sharing a pool of processors. This is an invaluable feature of PowerVM that is utilized when uncapping partitions. Uncapping partitions allow these partitions to tap more processor horsepower during peak periods of utilization, a really big help in workload-crunch situations. Multiple shared processor pools provide that much more versatility when virtualizing your CPUs.

PowerVM Enterprise includes everything in the Standard edition, as well as live partition mobility – a new feature of the Power6. Only the Power6 is supported by the Enterprise edition. Live partition mobility allows running virtual machines to migrate to another physical server running PowerVM. This is especially useful during periods where customers have planned outages.

PowerVM Lx86
PowerVM Lx86 is a technology that is wrapped around PowerVM which allows running most 32-bit x86 Linux applications on a System p without a recompile or a port. Prior to the introduction of PowerVM Lx86, you needed to compile your x86 Linux software to run on the System p architecture. This technology vastly increases the server consolidation opportunities that are now available, because it allows consolidation of x86 Linux applications. More than ever before, the System p has become an environment that allows moving away from distributed cluster-based x86 servers to larger centralized server farms – based on the System p.

Regardless of what edition you'll be using – make sure you look at the recently released Linux for pSeries Service aids for hardware diagnostics. The service aids allow system administrators to extract valuable information from the robust pSeries service processor for problem determination and servicing. Many of the commands packaged inside the service aids are very similar to the commands that you may find in AIX. You'll also find lots of specific filesets and other types of information for all types of supported distributions.

Sure, LoP is not for everyone (especially small shops with only a few x86 boxes), but for environments that require maximum availability, performance and support, it may just be what you are looking for.

ABOUT THE AUTHOR: Ken Milberg is a systems consultant with two decades of experience working with Unix and Linux systems. He is a Ask the Experts advisor and columnist.

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