Clarifying Minimum Required ESX Hosts for VCF Deployments

The VMware Cloud Foundation (VCF) 9.x Installer includes a built-in resource calculator that automatically determines the required compute and storage resources, along with the estimated number of ESX hosts needed to support the selected deployment configuration.

Understanding the compute and storage requirements is fairly straightforward, but the minimum number of ESX hosts required for a deployment is not always as clear, especially when factoring in the different supported principal storage types (vSAN, NFS and VMFS on Fibre Channel).

The official VCF 9.x documentation states the following:

Simple (non-HA)

While the documentation is absolutely correct when specifying the minimum host requirements for both Simple and High Availability deployments, there is a small nuance in how the minimum number of hosts is calculated for the High Availability deployment model.

The primary driver behind the four-host requirement is actually NSX Manager. In a High Availability deployment, NSX Manager uses anti-affinity rules to ensure each node is placed on a separate ESX host, allowing the service to remain available even during ESX upgrades.

In addition, customers can also choose different availability configurations for specific VCF components when using the JSON deployment method, which is not always apparent when using the VCF Installer.

Here is a quick summary of the nuance in practice when it comes to minimum ESX host requirements:

• If NSX is deployed in Simple mode (single node), which has been supported since VCF 9.0, while VCF Operations and VCF Automation are deployed in High Availability mode, the deployment can require as few as three or even two ESX hosts depending on the selected principal storage type, assuming sufficient compute resources are available.
• If NSX is deployed in High Availability mode (three nodes), regardless of whether VCF Operations and/or VCF Automation are deployed in High Availability mode or the selected primary storage type, a minimum of four ESX hosts will always be required.

To achieve the first scenario using the VCF Installer UI, you can simple select Simple deployment whether you are creating a new VCF Fleet or Converting/Importing an existing and then you can scale out VCF Operations and/or VCF Automation as Day-N workflow. If you would like to have everything deployed with the desired availability configuration, then customize the availablity configuration using the JSON method of deployment, which will allow you to import a modified JSON deployment manifest without having to resort to using VCF Installer API