Operating Systems

Disk Numbering Schemes

The Linux Guest definition in Figure 5 provides a template you can use to manage guest creation. The 191 disk will contain a copy of the kernel, initrd, and parm files from the LNXADMIN guest as shown in Figure 6. The parm and other files can then be modified on the 191 disk to customize this guest.

Standardizing on a minidisk numbering scheme makes it easier to pick out the contents of each minidisk if something needs changes. Consider an example:

• 700s for the Linux base installation
• 800s for any type of middleware
• 900s for SWAPs and VDISK.


Always run USER DISKMAP on any change before DIRECTXA is run to ensure there are no overlaps in guest definitions.

Validate Success Criteria

Once the z/VM and Linux on System z test Logical Partition (LPAR) is set up and the application with any required data is installed, you can begin to validate the success criteria, which is how you prove the success or failure of the POC. Depending on the criteria chosen, you may have to gather several different types of key metric data. Don’t try to present all the minute details of the data that you gather, as it can quickly become cumbersome. Include a few charts that net out the results and provide them in an executive overview.

Besides gathering run-time data, a TCO analysis is usually required. This should include hardware and software acquisition costs, ongoing maintenance costs, network equipment costs, environmentals such as power and cooling, and staffing costs to engineer and operate the environments. Don’t forget to include environments other than production in your analysis, since you will have costs for development, testing, and quality assurance servers.

IBM can help with TCO analysis; it has done these with many customers that were contemplating a migration to Linux on System z. IBM has developed several tools to help quantify and assess a possible migration; some of the assessments are available free.

More Information

To learn more, see these resources:

• z/VM: Guide for Automated Installation and Service,  http://publibz.boulder.ibm.com/epubs/pdf/hcsk2c00.pdf
• RHEL 6.0 (February 2011) z/VM and Linux on IBM System z: The Virtualization Cookbook for Red Hat Enterprise Linux 6.0,  www.redbooks.ibm.com/Redbooks.nsf/RedbookAbstracts/sg247932.html?Open
• SLES 11 SP1 (February 2011) z/VM and Linux on IBM System z: The Virtualization Cookbook for SLES SP1, www.redbooks.ibm.com/Redbooks.nsf/RedbookAbstracts/sg247931.html?Open
• Experiences With Oracle Solutions on Linux for IBM System z,
• Architecting z/VM and Linux for WebSphere V7 on System z, http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP101803.

Acknowledgement: Special thanks to Gary Loll (z/VM and Linux on System z Implementation Specialist, IBM Jamestown, NY) and Jon F. von Wolfersdorf (Certified Advanced Technical Support [ATS], Americas, IBM Endicott, NY) for their contributions to this article.

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