For those of you still upgrading to Exchange Server 2007 or consolidating your Exchange Servers, and are considering some of the High Availability solutions, I have a clear recommendation:
Avoid Single Copy Cluster (SCC); Use CCR (Cluster Continuous Replication) or SCR (Standby Continuous Replication) instead!
- SCC is not a complete HA solution. There exists a single point of failure – the shared storage! In CCR or SCR, there are two replicas of the same data.
- You don’t need a shared storage for CCR or SCR
- You don’t need third-party replication software (such as Double-Take) to span the database over two data centers.
- Improved failover behavior when compared to SCC.
- Installation is easier than SCC, and you do not need to perform additional hardware validation because shared storage is not required.
- Easier to manage.
- Improve backup performance, by letting backups to run from the passive copy of the data
- Single Copy Cluster (SCC) is being discontinued in Exchange Server 2010
So, for all future Exchange 2007 HA designs, please keep this in mind!
Fig 1. (below) Single Copy Cluster
Fig 2. (below) Cluster Continuous Replication