Yes, the data in Simple Message Queue (formerly MNS) is reliable. This topic describes how Alibaba Cloud ensures the reliability of data in SMQ.
SMQ stores all queues and messages in Alibaba Cloud data centers that feature high reliability and high availability. SMQ provides redundant storage to protect messages in queues during a hardware or network failure of one server. This means that copies of messages are stored on multiple servers. If a hardware or network failure occurs on one server, workloads are automatically switched to another server.