What-If Analysis is a feature of vRealize Operations that allows you to plan for an increase or decrease in workload or capacity requirements in your virtual infrastructure. You can use What-If Analysis to evaluate the demand and supply for capacity on your resources, and to assess the potential risk to your current capacity. You can create scenarios for adding and removing workloads, hosts, clusters, or datastores, and see the impact on the time remaining and capacity remaining scores12.

Time remaining and capacity remaining are two metrics that measure the available capacity in your environment. Time remaining is the estimated time until a resource runs out of capacity based on the current utilization and growth trends. Capacity remaining is the percentage of unused capacity that is available for future growth. Both metrics are calculated for CPU, memory, disk space, and network bandwidth resources34.

By using What-If Analysis, you can accomplish the goal of determining how many more ESXi servers are needed to increase the time remaining and capacity remaining scores. You can create a scenario for adding ESXi servers to a cluster or a datacenter, and specify the number, type, and configuration of the servers. You can then see the projected time remaining and capacity remaining scores for the cluster or the datacenter after adding the servers. You can also compare the results with the current scores and the recommended scores. You can adjust the number of servers until you reach the desired scores5 .

References:

1: What-If Analysis: Modeling Workload, Capacity, or Migration Planning 2: Create a What-If Scenario 3: [Capacity Overview - VMware Docs] 4: [Time Remaining and Capacity Remaining Metrics] 5: [Add Hosts to a Cluster or Datacenter Scenario] : [View the Results of a What-If Scenario] : vRealize Operations Manager User Guide : vRealize Operations Manager Installation and Configuration Guide : [vRealize Operations Manager Concepts Guide] : [vRealize Operations Manager Administration Guide] : [vRealize Operations Manager Customization and Extensibility Guide] : [vRealize Operations Manager Troubleshooting Guide] : [vRealize Operations Manager API Programming Guide] : [vRealize Operations Manager Certification Exam Guide]