Error: "There are currently 2 usable fault domains. The operation requires 1 more usable fault domains."

Products

• VMware vSAN

Issue/Introduction

Symptoms:

The user cannot apply a default vSAN policy (FTT=1) to a VM. They get the error, "There are currently two usable fault domains. The operation requires 1 more usable fault domain."

Environment

• VMware vSAN 7.x

• VMware vSAN 8.x

• VMware vSAN 9.x

Cause

• This issue happened because the vSAN cluster is in a partitioned state, and the policy requires the vSAN to be in a healthy state and three fault domains if the user is trying to apply the vSAN default policy with FTT=1.

• When the user checks the vSAN skyline health check, they notice the vSAN cluster partition with one or more ESXi hosts in a different partition.

• In order to function properly, all vSAN hosts should be able to communicate properly with each other via the vSAN Network.

• If all ESXi hosts in the cluster cannot communicate, a vSAN cluster will split into multiple network partitions. For instance, sub-groups of ESXi hosts may be able to communicate with each other, but not with other sub-groups. 

Resolution

• The user needs to resolve the cluster partition. After resolving the cluster partition, implementing the vSAN policy would be successful.

• For more information on the cluster partition, please check the following knowledge base article.

Troubleshooting the vSAN Network

vSAN Witness appliance partitioned from the stretched cluster