What do you get when you add LCR, CCR, SCC and SCR? A very confused IT Manager!

I got a call from an IT manager today trying to spec out an Exchange solution for one of his companies that is moving from Novell GroupWise to Exchange. The customer has three sites and they have a requirement that if their connectivity between sites goes out that the users at each location would be able to continue to access their e-mail as well as send e-mail to each other.

So being the Exchange geek that I am I started spewing out the intricacies of LCR, CCR, SCR, SCC and I am pretty sure he was more confused than when we started talking. With all of the options and three letter acronyms what is a non-Exchange geek to do? Apparently not call me for advice!

To redeem myself I put together this guide on the availability options for Exchange mailbox server roles. This post is going to briefly describe each availability solution for Exchange.

• LCR - Local Continuous Replication. This is a single server solution to provide data redundancy. You can run all of the server roles on this however there are some caveats for public folders. To be effective this solution requires two external drive arrays and two array controllers to provide true redundancy.
• CCR - Cluster Continuous Replication. This is a two node cluster that relies on Microsoft Clustering Services. This does not require shared disk however would require a "witness" node. Other than the mailbox role, no other roles can be installed on the cluster. There active node of the cluster replicates all changes to a passive copy of the database. A minimum of three Exchange servers would be required (2 mailbox nodes and a non-redundant Client Access and Hub Transport).
• SCC - Single Copy Cluster. This is a minimum two node cluster that relies on Microsoft Clustering Services. This requires shared disk like a SAN and has a single copy of the data. A minimum of three Exchange servers would be required (2 mailbox nodes and a non-redundant Client Access and Hub Transport).
• SCR - Standby Continuous Replication (SP1). This allows replication of databases to other servers located anywhere on the Intranet. This replication can be done to and from any type of mailbox node (other than a mailbox server that uses LCR)

Now that we have the basic definitions set, look for four more posts in the next few weeks breaking down each of the mailbox high availability options for Exchange Server 2007 SP1.