ESX 3.5 CPU utilisation and licensing

[clarges]

Hi

I am trying to get to the bottomos an issue with a customer and have come accross some interesting queries which am lookign for assistance on. I have a SQL server running in our VMware farm configured with 1 CPU which on occasion is maxed out. In terms of licensing MS states that 1 virtual cpu (core) is the same as a physical cpu, so add a second virtual cpu to my sql box i need another licenses

From MS documents

"To help you take advantage of the resource allocation benefits that VM technology offers, all products in the Per Processor licensing model are licensed by virtual processor.[[1]|http://communities.vmware.com/post!input.jspa?communityID=2411&go=CreateNewDiscussion#_ftn1|_ftnref1] If you run the software in virtual OS environments, you need a license for each virtual processor used by those OS environments on a particular server, rather than all the physical processors in the server. If you run the software in physical OS environments, similar to the previous licensing, you need a license for each physical processor used by the physical OS environment."

So basically based on this assumption a sqlserver on a physical box with a quad core processer gets full use of the 4 quads but on a similar box in a virtual enviroment only gets use of a quarter of the processing power, is this correct??

my customer would like to know if there is any possibility of taking advantage of using more cores per virtual cpu rather than adding a second CPU? as discussed in the same microsoft document see below

Virtual Processors Have the Same Number of Cores and Threads as Physical Processors-Each Fraction of a Virtual Processor Counts as a Full Virtual Processor

This section is relevant if you are using Per Processor products on multi-core processor systems. For reliability and performance, VM technology can allocate resources from separate physical processors in the server to create a virtual processor for use by a particular OS environment. Under the updated licensing, virtual processors are considered to have the same number of threads and cores as each physical processor in the underlying physical hardware system. Microsoft is adopting this definition to enable you to take advantage of the licensing policy we announced in 2004 for multi-core processors.[[1]|http://communities.vmware.com/post!input.jspa?communityID=2411&go=CreateNewDiscussion#_ftn1|_ftnref1] If the physical processors in the server have two cores, for licensing purposes, each virtual processor also has two cores, even if the cores are allocated from separate physical processors.

[madda]

We had a similar discussion with our licensing provider (which I recommend you also have with yours, to get full clarity), and the upshot of the discussion was that you license for the physical processors in the hardware not in the VM. For instance if you had 2x dual core processors you only need 2 CPU licenses, which makes it the same as the physical model.

It gets confusing when your in a virtual environment, but basically if you have 2 VMs running on the setup above, you need 4 CPU licenses as those 2 pCPUs will be used twice, but you don't need a license for each core.

I recommend clarifying it from your license provider though, just to cover your own ass.

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Mark Atherton

[clarges]

Mark thanks for the response.

It can get pretty confusing, Microsft state that a virtual CPU is treated as a CPU in terms of licensing in that if you use a fraction of the core you pay the full amount, however they state you can combine cores into a virtual CPU up to the amount in the physical machine and only pay for the 1 CPU license, but in ESX you cannot combine cores into one virtual cpu, so you are creating a second virtual cpu and this is were the grey area comes into play.

[madda]

Before they announced their VM licensing changes it was technicially illegal to use VMotion as you were transferring the licenses between hosts, and it all became a bit of a grey area.

Their license terms are based upon their own virtualisation software, rather than ESX so then the license terms become confusing. If you get your licensing provider to clarify the position, that should cover yourself.

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Mark Atherton