Exchange Server 2007 Service Pack 1 introduces the standby continuous replication (SCR) feature for high availability. SCR enables you to use continuous replication to replicate Mailbox server data from a stand-alone Mailbox server, or from a clustered mailbox server in a Single Copy Clusters (SCC) or Cluster Continuous Replication (CCR) environment.

SCR can be used to replicate a storage group in the primary data center to a remote location known as the secondary data center. The remote, or secondary, data center could contain a passive server that hosts what we call the SCR target. If the primary data center fails or is otherwise lost, the SCR target hosted in this standby can be quickly activated.

For SCR scenarios, see Standby Continuous Replication.

SCR is designed largely for data center recovery. This is important for service providers with multiple remote physical data centers and the data centers are in different Active Directory sites. SCR minimizes network bandwidth, and there is no distance limitation or single subnet requirement.

SCR enables standby configurations with the following advantages:

• No clustering required between servers
  
• No single subnet requirement
  
• Multiple Active Directory sites span