Microsoft Exchange Server 2013: Connectivity, Clients, and UM

High availability and Exchange transport

High availability has long been an important focus for the Exchange product group. An email system that can’t store and retrieve mail reliably isn’t much use to anyone. This focus has led to the release of several generations of high availability (HA) and disaster recovery (DR) features, beginning with transaction logging and continuing through storage groups, local and cluster continuous replication, and the DAG architecture. In Exchange 2007, the Exchange team broadened its definition of what HA means by adding a system for protecting messages against data loss in transit. Consider when server A is sending a message through SMTP to server B. If server A fails before the message is completely delivered, ...