Contention versus utilization

Because each layer has its own set of requirements, this translates into two sets of counters or metrics. Each group has its own metrics.

At the VM layer, we care whether a particular VM is being served well by the platform. Other VMs are irrelevant from the VM owner's point of view. So the key counter here is VM contention. Infrastructure metrics are irrelevant here. Only when we are satisfied that there is no contention can we proceed to check whether the VM is sized correctly or not. Most people check for utilization first because that is what they are used to monitoring in the physical infrastructure. In a virtual environment, we should check for contention first.

At the Infrastructure layer, we care whether it serves everyone well. Make sure that there is no contention for resources among all the VMs in the platform. Only when the infrastructure is clear from contention can we troubleshoot a particular VM. If the infrastructure is having a hard time serving a majority of the VMs, there is no point troubleshooting a particular VM. Notice all the previous sentences are about the VM. Yes, the Infrastructure counters are not that relevant.

Showing every single VM in a single screen is certainly impossible; hence, we need to have a metric that can track across all VMs. As you can guess, this metric does not exist in vSphere. vRealize Operations complements vSphere by allowing you to create super metrics. As you will see in the next four chapters, we use super metrics extensively.

Note

Super metrics allow you to get the big picture without losing the details.

This two-layer concept is also implemented by vSphere in compute and storage architectures. For example, there are two distinct layers of memory in vSphere. There is the inpidual VM memory provided by the hypervisor, and there is the physical memory at the host level. For an inpidual VM, we care whether the VM is getting enough memory. At the host level, we care whether the host has enough memory for everyone. Because of the difference in goals and because existing metrics in vSphere cannot provide the insight, we need to rely on vRealize Operations super metrics.