The Reliable Actors runtime manages scalability and reliability of Actors by distributing Actors throughout the cluster and automatically migrating them from failed nodes to healthy ones when required.

Actors are distributed across the partitions of the Actor Service, and those partitions are distributed across the nodes in a Service Fabric cluster. Each service partition contains a set of Actors. Service Fabric manages distribution and failover of the service partitions.

For example, an Actor service with nine partitions deployed to three nodes using the default Actor partition placement would be distributed like this:

The partition scheme and key range settings are taken care of by the runtime. Unlike Reliable Services, the Reliable Actors service is restricted to the range partitioning scheme (the uniform Int64 scheme) and requires you to use the full Int64 key range. By default, Actors are randomly placed into partitions resulting in uniform distribution. Communication between Actors happen over the network, which may introduce latency.