With the introduction of Exchange 2010 DAS has become a truly viable option for Exchange mailbox storage. Specifically, Exchange high availability improvements make DAS a viable option. In Exchange 2010 Microsoft introduced Database Availability Groups (DAG) as an improvement over Local Continuous Replication (LCR) Continuous Cluster Replication (CCR) and Standby Continuous Replication (SCR). This improvement meant that each individual mailbox database could have up to sixteen copies. As a result the need for protection against disk failure takes on less importance, hence the viability of DAS as a storage option for Exchange 2010.