What are the differences between the IoT Hub offers?
There are two categories of IoT Hub offers:
Stateful provides full MQTT protocol support.
Stateless provides a subset of MQTT protocol, generally speaking, the broker will not store any data on your behalf. This excludes the following MQTT messages: Publish QoS 2, Subscribe QoS 1-2, Retained messages and Will messages. Persistent sessions are also disabled.
The following plans are currently available:
Shared Plan (stateless): Devices are connected to a virtual broker that runs on a broker that is shared with other customers. Isolation is provided natively through the virtual broker mechanism.
Dedicated Plan (stateful): The broker is provided with dedicated CPU and memory resources and you can use them as you wish. There is no limitation in the usage of the broker, everything is dedicated to you.
High Availability Plan (stateful): Two dedicated brokers, connected together, are provided to avoid service interruption if one of them fails.