VCF Operations What-If Analysis Output

If you've done any capacity planning in VCF Operations you've likely used the What-If Analysis planning tool. It can be used for all sorts of use cases: adding/remove VMs from a Cluster, adding/removing ESX Hosts from a Cluster, and more. It'll provide Scenario Results that look something like this.

In this case I'm running a Scenario to determine Cluster Capacity should I remove 1 ESX Host from it. The graphs confuse people from time to time, so let's go through them.

First, you'll notice we provide both Demand and Allocation based responses, based on whatever Capacity metrics you might be using.

Looking at things in a bit more detail, I can see at the top: "After removing hosts your time remaining will still be 0 days". Why? Because as you can see bottom right I won't have enough Disk left based on my Disk Space Allocated metrics. Let's go through one of these graphs, we'll start with CPU Allocation.

A few things to note here:

• The full bar represents Total Capacity, which in this case is 960 vCPUs

• The blue part of the bar represents the Used Capacity, in this case 240 vCPUs

• The dark part of the bar represents Available Capacity, in this case 720 vCPUs

• The red lined part of the bar represents Removed Capacity (the amount that will be removed based on the Scenario), in this case 320 vCPUs

• The 400 vCPUs of 640 vCPUs represents the Available Capacity (720 vCPUs - 320 vCPUs) of Total Capacity (960 vCPUs - 320 vCPUs) after running the Scenario (removing the ESX Host)

In this case we have enough CPU Capacity to remove the ESX Host. The visual in this case helps us see that if/when we remove the ESX host we'll have enough remaining CPU Capacity to handle it (as represented by the space between the blue bar and the red lined part.

Looking at Disk tells a different story.

I'm showing both Demand and Allocation models to show the differences. The top graph indicates we have enough remaining Disk Space after the removal of our ESX Host, as shown by the dark part of the graph between the blue part and the red lined part. In this we'll have 452GB out of 4.42TB remaining.

In the bottom graph since all Disk has been allocated, there will be nothing remaining should you remove the ESX Host as indicated by the 0GB out of 4.42TB remaining.

Hope this was helpful, enjoy!