The Virtual Actor model implemented in Orleans differs from what OTP & Akka offer in that Virtual Actors have managed lifecycles and are never created or destroyed. Instead, they are activated when needed (fetching state from storage if needed) and deactivated when idle.

This helps you to reason about your system. You can never know if a node will fail at any point in time (in any system), but with Orleans you can be sure that an actor will be reactivated on a surviving node in event of a failure. In other words, you can continually message actor X without worrying about ever having to reinstantiate it on another node due to failure.

By default, Orleans maintains an eventually consistent mapping of actors to nodes (called silos) and relies on the storage layer to give strong consistency. Most of the default storage providers offer strong consistency.

By the way, Service Fabric includes an implementation of Virtual Actors which differ in a couple of ways: 1. The actors are placed using consistent hashing. Actor Ids are mapped to a range of partitions, the replicas of which can be moved between nodes in case of failure. 2. Actor state is physically stored on the actor node by default. Because Service Fabric uses distributed consensus to implement stateful services, they can persist each actors state in the partition which it belongs to. The state is replicated to a quorum of replicas on each write.