It’s also important to analyze whether the product or the function is the critical item. Often alternatives exist. You need to take into consideration whether the cost of migration — the disruption, training, client reconfiguration, etc. — is worth more or less than the return. The term “best-of-breed” has been overused in the computing industry; “good enough” is often sufficient. Therefore, even if an alternative product lacks features or functions, it may be sufficient to justify a migration. Be aware, however, of “hidden uses,” where groups or departments use products in unanticipated but important ways. These can completely derail a migration if not ferreted out and understood in advance.
When asked, “Why aren’t we using Linux?” the usual response is, of course, the question, “What should we use it for?” The good and bad news is that there are many answers to this; the good news is that there’s a fair chance that several choices make sense for you. The bad news is that you have to winnow those choices!
Organizations use Linux on zSeries in varied ways, and usage is rapidly evolving. Eighteen months ago, common uses were “infrastructure” applications such as Domain Name Server (DNS), file and printer sharing, e-mail, etc. While these are still excellent choices, static (HTML) and now dynamic Web serving (IBM WebSphere, BEA WebLogic, et al.) quickly entered the picture, and now applications of all types are available.
Vendor products such as IBM DB2 Connect, Oracle, and mail solutions from Bynari and Steltor (now Oracle Collaboration Suite) have made strong inroads. Common open source applications include the Apache Web server with its plethora of add-ons, and Samba for file and printer sharing.
Poor choices for mainframe Linux are CPU-intensive applications. Intel MIPS are far cheaper than zSeries MIPS, and are better choices for such uses.
IBM maintains a list of vendor products available for Linux on zSeries (see the sidebar for more details).
LINUX AND z/VM: A SOLID MARRIAGE
As discussed earlier, virtualizing Linux machines under z/VM on zSeries offers great promise for cost savings. Like any such marriage, however, it introduces issues that must be worked out for a harmonious relationship.
VM network configuration is always a consideration, not because it is deficient or particularly difficult, but because it’s unfamiliar. The process differs from what Linux folks know. VM staff have traditionally not rearranged their networks all that often and are unfamiliar with the process. In addition, once VM itself is set up, external routing must be configured.