Tag Archives: vCPU

Host Only Supports 1 vCPU: Licensing?

I had a fun day resolving a licensing issue for a client.  This one was a little different than I had seen in the past.  The cluster in question is an eight node cluster running ESX 3.5.  The error message that I received when trying to perform a vMotion was “Unable to migrate from HostA to HostB: Virtual machine has 2 virtual CPUs, but the host only supports 1.  The number of virtual CPU’s may be limited by the guest OS selected for the virtual machine or by the licensing for the host.”

At first, I thought this might be an issue with the virtual machine being a 64bit Windows 2008 virtual machine with multiple virtual CPU’s.  After further review of the environment I discovered this issue was happening with all multi-processor virtual machines.  I also discovered that this issue was happening on six of the eight hosts in the cluster. Continue reading Host Only Supports 1 vCPU: Licensing?

Virtual CPU’s, CPU Ready and Applications Performance on vSphere

In general you cannot infer the performance of an application running in a VM from looking at the resource utilization profile of that application or of the VM itself. There are many reasons for this documented in the Performance and Capacity Management White Paper available on this site. Continue reading Virtual CPU’s, CPU Ready and Applications Performance on vSphere