VMware Certified Professional - Data Center Virtualization (VCP-DCV) Practice Exam

Monitoring vCPU over-commitment on an ESXi host is crucial to maintaining optimal performance. The two performance counters that best indicate vCPU over-commitment are Ready and Co-Stop.

The Ready time counter measures the amount of time a virtual CPU is ready to run but is unable to do so because the physical CPUs are busy serving other virtual machines. A high Ready time indicates that there are not enough physical CPU resources available to meet the demand of the virtual machines. This situation often arises when multiple VMs are sharing vCPUs, leading to contention, which is a direct result of vCPU over-commitment.

Co-Stop is another important counter specifically relevant in environments with virtual machines that are configured to run on multiple vCPUs. This counter indicates the amount of time that a virtual machine is waiting for other vCPUs within the same VM to be scheduled on physical CPUs. If a VM with multiple vCPUs has high Co-Stop time, this typically suggests that there is contention for the available physical CPU resources, which can occur when vCPUs are over-committed.

Together, high metrics in both the Ready and Co-Stop counters indicate that the ESXi host might be over-committed in terms of