Adding ESXi host to vCenter server fails with error "datastore conflicts with an existing datastore in the datacenter that has the same URL"

Products

• VMware vSphere ESXi
• VMware vCenter Server

Issue/Introduction

• ESXi host is showing "disconnected" in vCenter server 
• Attempt to add ESXi host back to vCenter server fails with below error, the datastore mentioned in the error is another datastore on another ESXi host and has nothing to do with the ESXi host being added to vCenter: 
  
  Datastore '<datastore name>' conflicts with an existing datastore in the datacenter that has the same URL (ds://vmfs/volumes/<datastore UUID>/), but is backed by different physical storage.
  
  
• The host is added to vCenter server with FQDN

Environment

VMware vCenter Server 7.x
VMware vCenter Server 8.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Cause

The DNS record is incorrectly configured for the ESXi host that is disconnected from vCenter server.

The FQDN of the ESXi host is incorrectly mapped to the ip address of another ESXi host in the same vCenter server. As a result, when adding the ESXi host back to vCenter server, it's actually adding the same host that already exists in vCenter a second time and in turn fails with datastore conflict error. 

Resolution

Correct the DNS record configured on DNS server and then re-add ESXi host to vCenter server.

The DNS record can be verified with "nslookup <host FQDN/ip>" command on vCenter server.

If DNS isn't currently configured correctly, and /etc/hosts/ files on the hosts are being used, reference Adding/Deleting/Editing a host entry on vCenter server or ESXi host using vi editor - using this format for entries:

<IP address> <FQDN> <shortname>