VMware Aria Operations What-If Analysis Stacked Scenarios

You'd like to allocate more CPU, Memory, and Disk to several VMs in a vSphere Cluster, but you're not sure they'll fit, what to do? First place I'd look is the Cluster Capacity dashboard, this comes out of the box.

The Clusters Capacity Widget will show you how much capacity remains in each Cluster. Maximizing that widget will show you all of the data without scrolling.

Another option is to go to the Cluster object itself and explore the Capacity tab.

Here you can see exactly how many more VMs will fit in the Cluster, how much CPU, Memory, and Disk you have remaining, and more. I'm also using Custom VM Profiles here to see how many more "sized" VMs will fit into this cluster. We explored this previously here.

Finally, we can use the What-If Analysis feature in Plan - Capacity to see exactly how many more re-sized VMs will fit. We will use a stacked scenario: first remove the existing VMs, then we'll add them back in at their new sizes to confirm they'll fit. Here's how you do it: go to Plan - Capacity - What-If Analysis - ADD, then select REMOVE VMs for your use case. In my case this will be REMOVE VMs in the Workload Planning: Hyperconverged tile, as I'm running in a vSAN environment.

Give your Scenario a name, select the Datacenter and Cluster you want, Import from existing VMs (meaning your scenario will remove existing VMs), which you then select. In my case, I'm going to remove these 10 VMs.

Click RUN SCENARIO to get the details.

The Scenario Results will show how much CPU, Memory, and Disk will be left if/when you remove these VMs. Click SAVE top right to save this Scenario.

Next, run another scenario to add the newly sized VMs. Go back to Plan - Capacity - What-If Analysis - ADD, then ADD VMs for my use case. I'm increasing these 10 VMs to 6 vCPU x 32GB RAM x 100GB Disk.

Click RUN SCENARIO and get the details.

Projected CPU, Memory, and Disk utilizations are visible. Click SAVE top right. We now have both scenarios.

Select both, click the three dots.

Select Run.

Which will give you a preview, then click RUN SCENARIO.

Clicking through the CPU, Memory, and Disk tabs shows you how much capacity you'll have left after adding the newly resized VMs. The capacity analytics engine in Aria Operations is powerful, for more information on it check out this video from the VMware Cloud Management YouTube channel, enjoy!