vRealize Operations 6.2 Overhead Calculation

If you opened up the vRealize Operations Manager Analysis page in the latest version, you will notice it looks considerably different than it has in the past. Previously, you would expect the overhead and demand to show a smaller line than usage. In vRealize Operations Manager 6.2, they have changed the calculations for overhead, which I will walk you through.

The new overhead calculation is Total Capacity - Configured Capacity, the description of total cpacity in vCenter shows Total amount of memory reservation used by and available for powered-on virtual machines and vSphere services on the host. The new overhead model is basically taking the amount of memory that is left over after accounting for all the memory being consumed by virtual machines, vSphere services on the host, and VMkernel core functionality, such as device drivers and other internal uses and subtracting that from the configured capacity.

In the vSphere Web Client; select a host, click on Monitor, and then select the Performance tab. We are going to want to change our view to Memory and then select Chart Options.

In the Chart Options, I have unselected all the counters except Total Capacity.

In the image below, we can see that the total capacity available for powered-on virtual machines and vSphere services is on average 7480 MB.

If I subtract this from the configured capacity of 15930 MB, I have a remaining amount of 8450 MB, which is the overhead that is being used by ESXi and the virtual machines.

If I move back to vRealize Operations Manager, we notice that the overhead is 8.63 GB or roughly 8427 MB.

If you want to dive a little deeper into overhead, you can go back to the vSphere Web Client or vRealize Operations Manager All Metrics, then look at reservedCapacity which is the total amount of memory reservation used by powered-on virtual machines and vSphere services on the host including overhead amount; and sysUsage which is the amount of machine memory used by VMkernel for core fuctionaly, such as device drivers and other internal uses, it does not incude memory used by virtual machines or vSphere services.