What’s New in Exchange 2007 #12 of 15: High Availability in Exchange 2007
Posted by our Guest Blogger Peter Bruzzese, Exchange 2007 trainer for www.cbtnuggets.com.
In Exchange 2007, high availability comes in three flavors. Each offers a different level of protection, with different hardware and software requirements.
LCR. A single-server solution, LCR uses asynchronous log shipping and replay from one set of disks, and more specifically from a Storage Group (SG) with one database to another disk. It requires a manual switch to move from the primary copy of the data in the active SG to the secondary copy in the passive SG
CCR. CCR is a clustered solution that requires…
…only two nodes in the cluster, where one is the active node and the other is the passive node for automatic failover. This solution allows for two different systems and two different sets of storage, offering a greater level of availability because it eliminates single points of failure. Asynchronous log shipping and replay is used in this solution to keep the database up to date between the active and passive copies of the data. CCR is relatively easy to set up, in contrast to more complex, hardware-level geoclusters separated by great distances. However, one of the limitations to CCR (really of Windows Clustering) is that you either have to configure the cluster of both servers within a single datacenter or stretched between two datacenters if they are both using the same IP subnet. This limitation will be handled in Windows Server 2008.
Single copy cluster (SCC). SCC offers a similar solution to what Exchange Server 2003 offered. That is multiple systems with a single SG that's shared between the cluster nodes. Again, we have one active server with one or more passive servers waiting for a failover. Because SCC doesn’t provide a redundant SG, it doesn’t use log shipping and replay.
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