Intel 170 Servers Linux on iSeries Performance, Summary, Basic Requirements -- Where Linux Runs

Chapter 13. Linux on iSeries Performance

13.1 Summary

Linux on iSeries expands the iSeries platform solutions portfolio by allowing customers and software vendors to port existing Linux applications to the iSeries with minimal effort. But, how does it shape up in terms of performance? What does it look like generally and from a performance perspective? How can one best configure an iSeries machine to run Linux?

Key Ideas

y"Linux is Linux." Broadly speaking, Linux on iSeries has the same tools, function, look-and-feel of any other Linux.

yLinux operates in its own independent partition, though it has some dependency on OS/400 for a few key services like IPL ("booting").

yVirtual LAN and Virtual Disk provide differentiation for iSeries Linux.

yShared Processors (fractional CPUs) provides additional differentiation.

yLinux on iSeries provides a mechanism to port many UNIX and Linux applications to iSeries.

yLinux on iSeries particularly permits Linux-based middleware to exploit OS/400 function and data in a single hardware package.

yLinux on iSeries is available on selected iSeries hardware (see IBM web site for details).

yLinux is not dependent per se on OS/400 releases. Technically, any Linux distribution could be hosted by any of the present two releases (V5R1 or V5R2) that allow Linux. It becomes a question of service and support. Users should consult product literature to make sure there is support for their desired combination.

yLinux and other Open Source tools are almost all constructed from a single Open Source compiler known as gcc. Therefore, the quality of its code generation is of significant interest. Java is a significant exception to this, having its own code generation.

13.2 Basic Requirements -- Where Linux Runs

For various technical reasons, Linux may only be deployed on systems with certain hardware facilities.

These are:

yLogical partitioning (LPAR). Linux is not part of OS/400. It needs to have its own partition of the system resources, segregated from OS/400 and, for that matter, any other Linux partitions. A special software feature called the Hypervisor keeps each partition operating separately.

y“Guest” Operating System Capability. This begins in V5R1. Part of the iSeries Linux freedom story is to run Linux as Linux, including code from third parties running with root authority and other privilege modes. By definition, such code is not provided by IBM. Therefore, to keep OS/400 and Linux segregated from each other, a few key hardware facilities are needed that are not present on earlier models. (When all partitions run OS/400, the hypervisor’s task is simplified, permitting older iSeries and AS/400 to run LPAR).

In addition, some models and processor feature codes can run Linux more flexibly than others. The two key features that not all Linux-capable processors support are:

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
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