What are three requirements to set up AppDynamics Controllers as a high availability pair?

To set up AppDynamics Controllers as a high availability pair, you need to meet the following requirements1:

Passwordless SSH must be configured between the two Controller servers. This allows the Enterprise Console to automate the configuration and administration tasks associated with a highly available deployment on Linux systems.

Both servers must have the Controller software installed prior to setting up high availability. The Controllers in an HA pair must be equivalent versions, and be in the same data center.

Both servers must have identical directory structures for the Controller installation. The individual machines in the Controller HA pair need to have an equivalent amount of disk space. References: Prerequisites for High Availability