Exchange 2007 provides high availability through four models; Local continuous replication, Single copy cluster, cluster Continuous replication and Standby continuous replication.
Exchange 2007 single copy cluster provides high availability for the node failure scenarios and can be implemented with at least two nodes in Active/Passive model. This is very much similar to the Exchange 2003 cluster setup where shared storage is used between the nodes and storage group resides on that shared storage.
I have been to couple of customers where there were complains cluster of shifting and dismounting of the databases. I have started checking and found that resources dependency model on those Exchange 2007 clusters were not configured as per the recommendations. Resource dependency model in Exchange 2007 Single copy clusters were implemented like exchange 2003 conventional cluster although it is changed in Exchange 2007 single copy clusters.
I have found that for both of the customers were not having physical disk resources in the dependency for the Exchange 2007 database instances. I have also found that for one of the customer “Affect the group” option for the Microsoft Exchange information store resource were not set to its default value and it was enabled.
Correcting and comparing the whole resource dependency model for Exchange 2007 Single copy cluster according to the best practices alleviated many pains to the customers and helped them to avoid critical situations.
Following articles could be used for further details and comparisons against the recommended configurations.
Configuring Disk Dependencies
Farooq Ahmed from NEPA team.