How can the architect implement high availability?

Implementing high availability by configuring three distinct high-availability pairs-one pair within the New York datacenter, one within London, and one within Hong Kong-ensures redundancy and resilience against local failures at each site. This design allows for immediate failover within a datacenter if an appliance fails, maintaining local service continuity.

Configuring high-availability pairs between geographically distant datacenters, such as New York and London, is impractical and unreliable for standard HA due to the high-latency and low-bandwidth requirements for HA synchronization and heartbeat, making cross-datacenter HA prone to split-brain scenarios.

Configuring only two high-availability pairs across three datacenters is insufficient for robust HA, as it would either leave one datacenter without local redundancy or attempt to stretch HA across WAN links, which is not a recommended design for maintaining local site resilience.

Configuring one cluster instance containing all six appliances across three geographically dispersed datacenters is technically unsound. Clustering requires low-latency, high-bandwidth interconnects and is not designed to operate reliably over global WAN links, which would lead to instability and poor performance.