vSAN host fails to enter Maintenance Mode with 'Full data migration' option selected with the error "There are currently X usable fault domains. The operation requires X+1 more usable fault domains."

Products

• VMware vSAN

Issue/Introduction

• A host fails to enter maintenance mode using Full Data Evacuation with the error "There are currently X usable fault domains. The operation requires X+1 more usable fault domains."
• The host is part of a Standard vSAN Cluster.
• There are enough hosts in the cluster to support the Storage Policy in use by the objects. Please check the requirements below:

• The hosts are configured to be separated in Fault Domains and not as standalone hosts.

Environment

VMware vSAN 8.0.x
VMware vSAN 7.0.x
VMware vSAN 6.x

Cause

An insufficient number of Fault Domains are currently present in the environment for component placement.

Even though there are enough hosts in the cluster for the storage policy in use, when Fault Domains are configured on the cluster, the number of Fault Domains takes precedence over the number of hosts present.

Resolution

• Remove the Fault Domains and leave the hosts as "Standalone" hosts in the Standard Cluster. 
  1. Navigate to the vSAN cluster.
  2. Click the Configure tab.
  3. Under vSAN, click Fault Domains.
  4. Click the Actions icon on the right side of the fault domain, and select Delete.
  5. Click Delete to confirm.

All hosts in the fault domain are removed and the selected fault domain is deleted from the vSAN cluster. Each host that is not part of a fault domain is considered to reside in its own single-host fault domain.

 

• Or reconfigure the Fault Domains in a way that there will be enough of them once the required host is placed in Maintenance Mode - Full Data Migration.

Additional Information

Related Links:

VMware vSAN 8.0 - Managing Fault Domains in vSAN Clusters

vSAN -- Creating/Reverting Snapshots fails -- Fault Domain Error

vSAN host fails to enter Maintenance Mode with 'Full data migration' option selected