Types of clustering in exchange 2007:

This article explains the different types of clustering technology available with the exchange 2007 server. The exchange 2007 version has some new exciting features in terms of the high availability. It has four types of clustering and which has its own level of fault tolerance and availability. I have also added the diagram for better understanding.

1. Single copy clusters(SCC):

# This cluster type is similar to the one as in previous exchange versions. In fact it is exactly similar to the one in exchange 2003.

# Uses a single copy of database is shared between the nodes of the cluster.

# The database copy is stored in the SAN Storage device and also at any point of time the database will be owned by single node.

# Fault tolerance – There is chance of SOP i.e., Single point of failure. SCC environment works great if a node/server fails, but still Database failure in the SAN will cause the damage.

2. Local Continuous Replication (LCR):

# This is the new feature of exchange 2007.

# LCR is a single server solution which creates and maintains a copy of the database in the same server just like a mirroring concept.

# This cluster type provides usual log shipping, log replaying and can be switched to the mirror copy by manual action in case of any database issues.

# One prerequisite for implementing LCR is that Storage Group can contain only one database. So if you need to implement multiple databases you automatically need to implement multiple Storage Groups.

# This overcomes the drawbacks of single point of failure for database crashes, but it doesn’t help in server failure.

# Automatic failover will not happen, in case of database failure or any issue.

3.Cluster Continuous Replication (CCR):

# This is the new feature of exchange 2007. It is the best and highly improved version of clustering solution

# This cluster type is non-shared one, fault tolerant in terms of server and database front, high availability and site resilience. CCR is very different from clustering in previous exchange versions.

# CCR is a multi server solution which creates and maintains a copy of the database in the second servers in a failover cluster.

# CCR will automatically failover in case of any server related issues and also database related failures. So no need of manual switch action as in LCR.

4. Standby Continuous replication (SCR):

# This is the new feature introduced in exchange 2007 SP1.

# SCR is a clustered solution that is used to have the standby copies of the clustered server databases. As by its name, we can call as standby recovery servers.

# SCR uses the same log shipping and replay technology used by LCR and CCR. It is just getting seeded by and from either CCR or LCR cluster server.

# This is ideal for the situation like you need to recover from the complete site failure. We can call this for disaster recovery.

Hope the above is informative.

Thanks

Logan

971-552596187 logu_microsoft@hotmail.com