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Image: Is IBM Ditching the Processor Value Unit (PVU) Software License Metric?

IBM announced on April 12, 2011, a change for selected products whereby they are moving from the Processor Value Unit (PVU) software license metric to the new Resource Value Unit (RVU) metric. This impacts several product families such as Tivoli Monitoring, Tivoli Provisioning and Service Delivery Manager. PVU and RVU metrics are radically different:

  • With the PVU metric, the capacity of the server where the application is installed is measured. If this application is moved to another server or the hardware properties (processors) of the server hosting it are changed, the license may be impacted. This can easily happen in virtual server environments. So, there is a risk of being out of license compliance.
  • With the RVU metric, the number of units of a specific resource used or managed by the application are counted. The application can be freely moved across servers and the hardware properties (processors) of the server hosting it can be modified with no impact on the license.

This makes perfect sense:  the capacity of the server does not always correspond to the usage of the software installed on it. In the past, with the PVU metric, many IBM customers had to choose between price and performance when selecting hardware on which to install the software.  With the RVU license metric, IBM customers will be able to configure and adjust the hardware capacity of the server hosting the application to meet their business performance requirements: there will be no impact on license compliance or license cost.

What is a Resource Value Unit?  The purpose of the RVU license metric is to tie the number of licenses required, measured in RVUs, to the utilization of the software or the resources the software manages.  RVUs may use—the number of Gigabytes, premium income, pages per month, number of messages, etc., as units of measure. The price of the license is based on the number of RVUs required. The RVU calculation is quite complex and usually uses a factor that is applied per quantity tier. In the case related to this IBM announcement, the number of activated processor cores for physical or virtual servers managed must be counted for RVU licensing. The factor table is as follow:

For Servers (active cores):

Quantity Factor
0 to 2,500 1.00
2,501 to 10,000 0.80
10,001 to 50,000 0.60
50,001 to 150,000 0.50
Over 150,001 0.20

Example: if a customer has 45,000 Activated Processor Cores across its managed servers, it will need 29,500 RVUs.

  • (2,500*1.00 + 7,500*0.80 + 35,000*0.60)  = 29,500 RVUs

If the resource considered is a client device, the metric is just the number of client devices but a different factor table is applied. For managed servers, it is not that simple to get the right number of license entitlements needed, as it relies on a number of cores. It gets even more complex if the servers considered are deployed in virtual environments: the RVU license metric in this case supports sub-capacity licensing.  In these environments, the measurement of Activated Processor Cores is based on the number of processor cores available for use. Rules and definitions are clearly defined by IBM but are specific to each virtual environment (virtual machines or hardware partitions).

Overall, customers will benefit from the IBM announcement and the use of the RVU software license metric: they will purchase a license from IBM that will be calculated based on what they use. However, moving managed servers across hosts in virtual environments or modifying their hardware characteristics can impact the license position in cases where the RVU is based on active cores available in those managed servers. Staying in license compliance is not going to be easier.