Posted by martijnl on January 30, 2008
IBM licensing has had a real makeover about 18 months ago with the introduction of the PVU (Processor Value Unit). All prices are calculated per PVU which makes it easy to calculate your licensing fee once you have figured out the number of PVU’s you have.
In a virtualized environment however this poses the following challenges:
- In a heterogenous environment finding out the number of PVU’s requires you to count them based on the PVU table supplied by IBM: PVU Table. If you use single, dual and quad core CPU’s in your clusters this can become quite a task
- IBM does not recognize resource groups as a means of reducing the number of licenses. The current policy requires you to license the entire cluster that a Websphere virtual machine resides on. The reasoning behind this logic is that because of VMotion/DRS a server can be on any host using any resource so all should be licensed. Depending on the configuration of a failover environment it is possible that you need to license that failover environment as well.
- The above point could force unwanted or unnecessary design alterations as you need to take into account a seperate cluster for Websphere servers where you maybe wouldn’t want to do that. This could have VMWare and Websphere licensing and hardware consequences by increasing the number of necessary licenses and servers to create separate Websphere clusters.
- An example: if you have two dual core physical servers running Websphere and you use quad dual-core CPU hosts than you have a four fold increase in Websphere licenses even if you put them in a dedicated cluster. This logic evens out when you have significantly more Websphere instances but you will still need to take it into account as a design constraint and calculate how many hosts you need in the cluster for Websphere VM’s to ensure sufficient availability of resources for operation and a sufficient amount of resources for host failure.