Product : Citrix, XenServer/7.3, Enterprise
Feature : Cluster Size, HA/DR, VM Mobility and HA
Content Owner:  Roman Macek
Summary
16 hosts / resource pool
Details
16 Hosts per Resource Pool.
Please see XenServer 7.3 Configuration Limits document http://bit.ly/2rcrjZx
Note: the maximum pool size, for Free edition is now restricted to 3 Hosts.