It is highly recommended to use the Veeam MP for VMware Sizing Calculator included in the Veeam MP Resource Kit to estimate the number of Collectors required for your infrastructure.
The Resource Kit is included on the ISO image for Veeam MP.
Additional HA Considerations
To provide failover capability, in addition to the recommendation generated by the Sizing Calculator, you will need:
•One additional unloaded Inactive Collector (acting as warm standby)
•Sufficient headroom on existing Collectors to absorb the monitoring jobs of any failed Collector