A few days ago one of my Xen hosts died due to an issue with the raid controller. In order to revive it I had to rebuild it, and add it back into the pool. However there was a problem; the original entry for this host in XenCenter appeared in red, which indicated that it was disconnected, and another entry for the same exact host with the same exact hostname appeared next to it in the host list for this particular cluster. I was unable to remove the orphaned host via XenCenter as there was no remove option.
I was in a pickle.
However I was able to find a solution.
First and formost it appears that there are actually two ways to do this; the first one being from the Windows command line where you are running Xencenter, or on the master node in the cluster.
This example is from the Windows CLI. Note that the UUID that is output to the command line is the UUID of the Host that is unreachable — the orphaned host.
C:\Program Files\Citrix\XenCenter>xe -s <Hostname_of_master> -u root -pw <root_password> pool-sync-database
You attempted an operation which involves a host which could not be contacted.
host: 560e233b-0e8b-4c2f-a641-cf1876630a6b (virt04.atlc1)
C:\Program Files\Citrix\XenCenter>xe -s <Hostname_of_master> -u root -pw <root_password> host-foget uuid=560e233b-0e8b-4c2f-a641-cf1876630a6b
WARNING: A host should only be forgotten if it is physically unrecoverable;
WARNING: if possible, Hosts should be 'ejected' from the Pool instead.
WARNING: Once a host has been forgotten it will have to be re-installed.
WARNING: This operation is irreversible.
Type 'yes' to continue
Returning to XenCenter I found that the orphaned host entry had been removed.