VMs failing to deploy with "There are currently X usable fault domains. The operation requires X more usable fault domains."

Products

• VMware vSAN

Issue/Introduction

• 4 node/host cluster
• When trying to enable vCLS the VMs fail to deploy with error: "There are currently X usable fault domains. The operation requires X more usable fault domains."
• When trying to deploy VMs the same error is received
• Running Create VM Proactive test, the test fails 
• vSAN datastore is configured with the vSAN Default Storage Policy
• Multiple clusters have the vSAN Default Storage Policy set for their respective vSAN datastore

Environment

VMware vSAN (All Versions)

Cause

The vSAN Default Storage policy was modified for 2 failures to tolerate RAID1. A minimum of 5 hosts is required for 2 failures to tolerate RAID1.

Please refer to the following documentation regarding Fault Domains for further information on vSAN cluster sizing. For safety reasons, in its default configuration vSAN will not allow the provisioning of new objects if there are not enough resources to satisfy the applied storage policy.

Resolution

Clone the vSAN Default Storage Policy and set failures to tolerate back to 1. It's recommended not to change the default vSAN storage policies that are prebuilt into vCenter, rather clone/create new storage policies for your required needs.