Q

Linux on P5 systems

We have migrated numerous areas from HPUX to Linux over the past five years. We've done this primarily for TCO, more for the cost of hardware than the cost of the OS. Areas that we have deployed Linux over Unix (and over Windows) includes DNS, mail routing and scanning, student file/mail/Web storage (1.3TB SAN-based on RedHat AS4) and disk-to-disk backup storage.

We haven't moved everything away from HP-UX, Solaris and AIX for a couple of reasons:

  1. Some of our software vendors don't have a Linux solution
  2. Desire to have a single vendor to call for a solution (e.g., our backup solution is almost end-to-end HP)
  3. Concerns about robustness for Oracle on Linux
  4. Concerns about SAN failover drivers for our HBAs on Linux
  5. Potential hardware quality issues (commodity Intel hardware vs. higher-end PA-RISC/SPARC systems)

Is there any way around the aforementioned issues?

Absolutely there is. The solution is Linux on Power (LoP). IBM POWER5 processor-based systems (which include System p, System i and BladeCenter JS21servers and OpenPower) have been tuned for Linux by IBM engineers, offering features for Linux previously only available on their Unix and mainframe architecture. The tuning is done in areas including: RAS, virtualization, performance, scalability and reliability. The end result is a platform, specifically designed to dramatically improve your ability to manage and administer your systems.

IBM's challenge was to determine how businesses could gain these advantages, while at the same time continuing to take advantage of the quality of service achieved with Unix. The POWER5 architecture on Linux makes Linux a viable option for the most mission-critical applications. Both Red Hat and SUSE support Linux on the pSeries and you must use either SUSE Linux Enterprise Server 9 (SLES9) or Red Hat Enterprise Linux 4 (RHEL4) to gain all the virtualization and tuning benefits, as they run with the ground-breaking Linux 2.6 kernel.

From a Linux perspective, IBM has partnered with Red Hat and SUSE to integrate enhancements into their most recent distributions to maximize the benefits of Linux on IBM's hardware. That allows Linux to exploit the processor hardware in ways it just could not do before. If you're going to migrate to LoP, you must understand the critical differences between the source and target platforms. It's important to note that just because you are migrating Linux from an x86 machines to System p, doesn't guarantee that it will work.

Here are several architecture-specific differences you should be aware of between x86 Linux and LoP:

  • Endianness/byte ordering
  • Data type length in 32- and 64-bit environments
  • Data alignment differences in the architectures

Endianness refers to how a data element and its individual bytes are stored and addressed in memory. Byte-ordering issues are often encountered by developers during the process of migrating applications, device drivers or data files from the x86 architecture to the POWER architecture.

IBM announced in December the delivery of the 2,500th Linux application available for POWER. The number of tested, native applications available for the Linux on POWER platform has grown more than 200% in the last two years.

Perhaps the best feature of all that you will get is Advanced Power Virtualization. (APV). You want the maximum flexibility you can have to share unused resources, allocate and logically partition your servers. With Advanced Power Virtualization (APV) support, you can do all that and more. Linux has always been at the forefront in terms of lowering total cost of ownership (TCO) on commodity-based PCs. Now, IBM is pushing the envelope. This is a major philosophical and architectural breakthrough; no other vendor can claim that it natively supports Linux and Unix on its high-end systems (forget VMware) at the same time. Sure, Sun can support Linux and even Windows on its servers, but not using its vaporware version of virtualization.

There's been talk about Zen and Solaris (similar to what Red Hat is trying to do with RHEL5), but right now it just doesn't exist. With the micro-partitioning abilities of Advanced Power Virtualization (APV), you can assign as little as a tenth of a CPU to an LPAR. Shared Ethernet, an APV feature that lets you use virtual adapters on your partitions using VIO servers, further lowers TCO by removing the need for dedicated adapters in environments that may not need a lot of network bandwidth. A Shared Ethernet Adapter (SEA) can be used to connect a physical Ethernet network to a virtual Ethernet network. It also provides the ability for several client partitions to share one physical adapter.

System p allows you to run both Linux and Unix (AIX) on the same box at the same time, using logical partitions. Perhaps the best feature of LoP, is that it will give you the single source vendor option (IBM) that you desire; storage, OS support, hardware, etc. It will also give you the raw performance and reliability not yet seen available in traditional Linux shops.

This was first published in December 2006

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