"There are currently x usable fault domains. The operation requires 1 more usable fault domains." while taking virtual machine snapshot

Products

• VMware vSAN

Issue/Introduction

When trying to create a snapshot of a VM residing on a vSAN datastore, it fails with the error:

There are currently 1 usable fault domains. The operation requires 2 more usable fault domains.
An error occurred while taking a snapshot: Out of resources.

Or 

No disks of required version is present in the cluster for this operation to succeed. An error occurred while taking a snapshot: Out of resources.

Environment

vSAN Robo Cluster

Cause

In a 2-node stretched cluster with the default storage policy (FTT=1), witness configuration is essential. Since a witness is not configured in this setup, object creation is failing due to an insufficient number of fault domains—the policy requires a minimum of three fault domains.

Resolution

After adding the witness to the fault domain, the snapshot creation completed successfully.