Whereas Exchange 2003 really offers only one type of clustering support (local, with multiple servers sharing a SAN), Exchange 2007 supports log shipping both remotely and locally, which opens up new modes of clustering:
* Local Continuous Replication (LCR), a single-server solution in which the system uses the logs to create a second copy of a storage group (SG) on a different set of disks. This method gives you a second copy of the data. For more information about LCR, go to http://technet.microsoft.com/en-us/library/bb125195.aspx.
* Cluster Continuous Replication (CCR), a two-server solution in which the system ships the logs to a second server to maintain a second copy of the SG. This second server can be local or remote. For more information about CCR, go to http://technet.microsoft.com/en-us/library/bb124521.aspx.
* Single Copy Clusters (SCC), the same idea as Exchange 2003 clusters, in which one set of data is connected to multiple servers. For more information about SCC, go to http://technet.microsoft.com/en-us/library/bb125217.aspx.