Linux can help with several of these issues, and Linux on zSeries can help with them all.
Linux, still a relatively small system, runs effectively on low-end hardware. Many installations have earned their Linux stripes by installing a downloaded copy on an unused 486 or low-end Pentium that was gathering dust, proving viability of the intended use, and then moving it to larger platforms (or not!) as the need arose.
While zSeries hardware is hardly “low-end,” its superior resource controls mean that virtualizing Linux under z/VM on zSeries often dramatically reduces raw MIPS required. (Linux can, of course, run in an LPAR, but the fixed hardware allocation and restrictions on the number of images usually make this unpalatable for other than short-term use.) Some analysts estimate that the average distributed server runs at less than 10 percent utilization, with the rest of the processing power reserved for growth or peak usage. Anyone who has stressed even a high-end Intel machine knows that when the machine is busy performing two or three tasks, there’s little point in trying to get it to do anything else — you just have to wait.
On the other hand, well-run mainframes often run at 100 percent utilization while providing excellent response to thousands of applications and interactive users. This means that server consolidation using Linux under z/VM can allocate resources using that 10 percent factor, leaving a global pool of extra resource for peak loads, and can measure and tune appropriately to provide required service levels.
Linux, of course, is free to acquire, as are many Linux applications. Even vendor applications for Linux typically have cheaper pricing models than traditional ISVs, based partly on the fact that the market won’t (yet?) support the older schemes, and partly on the vast numbers of free, open source applications. While many installations prefer vendor-supported products for reasons of support and service, the existence of alternatives means that, for once, installations often really can abandon a vendor perceived as rapacious. And, since “Linux is Linux,” almost any application that runs on an Intel machine will run on zSeries.
Smaller, cheaper hardware typically requires less in the way of facilities, although when Linux is being installed on Intel machines to replace Windows applications, the common distributed “one application per machine” approach works against this principle. On the other hand, when hundreds of Intel servers are consolidated onto Linux virtual machines on zSeries, facilities savings can be significant for the following items:
- Floorspace (one zSeries takes far less room than dozens of racks)
- Power and cooling
- Cabling (internal networking eliminates the need for a “rat’s nest” of cables among machines).