@nick-lloyd I think the answer would depend on the state of your XAPI database given the fact that each host thinks that it in the pool master. To convert one or more of the hosts to a slave, you would need to --

edit the file so that it contains slave:<IP address of master> instead of master run mv /var/xapi/state.db /var/xapi/state.db-old to get rid of the old xapi database reboot the host

Once rebooted, the xapi database will be regenerated by syncing with the pool master.