Remove a failed Xenserver from Pool

Run the following command to discover the UUID of the broken server:

xe host-list

Use the following command to remove the host:

xe host-forget uuid=<uuid_of_broken_server>

Note that a host should only be forgotten if it is physically unrecoverable, if possible, Hosts should be 'ejected' from the Pool instead.
Once a host has been forgotten it will have to be re-installed.

If the forget command fails with:

This host cannot be forgotten because there are some user VMs still running

Use this command to find witch VMs are listed as running on that server:

xe vm-list resident-on=<uuid_of_broken_server>

Then, for each VM returned by the previous command use the following command:

xe vm-reset-powerstate uuid=<VM_uuid>

Then try the forget command again.