Linux on IBM Z: Difference between revisions

 

==Pricing and costs==

Linux on IBM Z is not generally appropriate on-premises for small businesses that would have fewer than about 10 distributed Linux servers, although some expensive per-processor licensed software can quickly reduce that [[rule of thumb]]. Most software vendors, including IBM, treat the highly virtualized IFLs just like non-virtualized processors on other platforms for licensing purposes. In other words, a single IFL running scores of Linux instances still typically counts as one "ordinary" CPU, at the same CPU price, for software licensing. Test, development, quality assurance, training, and redundant production server instances can all run on one IFL (or more IFLs, but only if needed for peak demand performance capacity). Thus, beyond some minimum threshold, Linux on IBM Z can quickly become cost-advantageous when factoring in labor and software costs.

 

 

==Appropriate workloads==

Mainframe characteristics are designed for such business workloads as transaction processing (especially in conjunction with concurrent, high volume batch processing) and large database management. Mainframe design traditionally emphasizes "balanced" performance for all computing elements including input/output, implemented via [[channel I/O]]. Mainframes offload I/O, system accounting, and other non-core computing tasks from the main CPUs as much as possible, and z/Architecture additionally offloads cryptographic calculations. For example, in a single IBM z13 machine up to 141 processor cores are available to configure as IFLs. However, every such machine also has 27 additional main cores: 2 as spares, 1 for firmware support, and the remainder running system accounting and I/O support tasks. In addition, each I/O adapter typically has two [[PowerPC]] processors, and a z13 supports hundreds of I/O adapters. There are also separate processors handling memory and cache control tasks, environmental monitoring, and internal interconnections, as examples.