Many businesses are realizing the processing and failover benefits of incorporating clustered servers in their IT environments. Having groups of servers whose processing resources are shared and centrally allocated means that server malfunctions can be remedied without compromising business functions that otherwise might need to be suspended until the appropriate fix can be applied. It also means that the most mission-critical functions can benefit from prioritized allocation of processing power from multiple machines, often resulting in improved overall performance.
However, licensing software in clustered environments can carry with it pitfalls that many business may not suspect at the outset. IBM software licensed based on Processor Value Units (PVUs) is an excellent example. PVU-based licensing entails counting up the number of processor cores for a computer where software is to be installed, multiplying that number by the per-core PVU value assigned by IBM for the processor architecture in question, and then multiplying that number by the per-PVU MSRP for the software product. Thus, for example, an IBM 795-series server with a single quad-core POWER7 processor chip running IBM DB2 Enterprise database software would incur the following licensing obligation:
4 cores per server x 120 PVUs per core x $405.00 per PVU = $194,400.00 per server
However, unless the business qualifies for IBM’s sub-capacity licensing model (more on that below), the inclusion of that server in a server cluster means that each of those servers must be licensed to full PVU capacity for DB2 Enterprise as well. Worse, even if the cluster is comprised of numerous virtual servers, and only one of those virtual servers is the one where DB2 Enterprise is installed, the entire cluster nevertheless must be licensed for that product. Thus, though a business may only be deriving limited functionality from its DB2 Enterprise installation, if that installation is in an 8-server cluster where each of the physical servers is identical to the one shown above, that business could incur a DB2 Enterprise licensing charge equal to 8 times the above amount, or $1,555,200.00.
For this reason, it is vital that business operating IBM software in clustered server environments familiarize themselves with IBM’s sub-capacity licensing rules. Under the sub-capacity model, it is necessary to license a PVU-based software product only according to the number of activated processor cores accessed by that product. Thus, in the example above, if DB2 Enterprise is capped to a virtual server utilizing only 1 of the 4 availably physical cores , then the licensing charge is a quarter of the full-capacity server charge reflected above, or $48,600.00.
However, in order to utilize sub-capacity licensing, a business must agree to and abide by IBM’s contract terms for sub-capacity licensing, which include requirements for the technology used to cap the virtualized software deployments along with the obligation to maintain regularly generated records regarding the nature of those deployments. In many cases, it is necessary to deploy the IBM License Metric Tool (ILMT) to generate those records.
IBM software licensing can be a complex undertaking. When doubt arises, it is well worth it to seek the assistance of knowledgeable licensing counsel.