In my recent posts I discussed the fundamentals of Exchange Server 2007 high availability and how to use Local Continuous Replication.  In this post I will demonstrate one of the two Exchange Server 2007 clustering methods, Single Copy Clusters.

What are Single Copy Clusters?

Single Copy Clusters (SCC) for Exchange Server 2007 is basically the same as clustering in previous versions of Exchange Server.  Two cluster server nodes connect to shared resources in an active/passive configuration.  The two servers appear to other computers to be a single system, and when one server node fails the clustered resources are able to fail over to the other node and continue operation.

SCC provides high availability for the Mailbox Server by protecting it from the failure of either cluster server node.  Typically the cluster will also consist of redundant networking (e.g. teamed network interfaces, multiple switches) and storage components (e.g. a SAN that is in itself a highly available system through redundant components).  The servers are also usually located in high quality data centers with redundant power and cooling.

SCC is available in the Enterprise edition of Exchange Server 2007.  Because it uses an underlying Windows Server failover cluster, the servers that form part of the cluster must also run the Enterprise edition of Windows Server (either 2003 or 2008).

Unlike LCR an SCC cluster offers high availability benefits but no performance benefits.  Because there is a single copy of each mailbox database within the cluster there is no opportunity to use a passive copy for backup operations.

How to Install a Single Copy Cluster

In this example two Windows Server 2003 Enterprise edition servers have been configured with the basic requirements of a failover cluster:

• A public network interface for normal network operations
• A private network interface for the cluster “heartbeat”
• Shared disk storage for the database, log files, and cluster quorum disk

Once the failover cluster has been configured we can install Exchange Server 2007 on the first node.  Run setup as normal, and when selecting the roles to install choose “Active Clustered Mailbox Role” as the server role.  You will notice that a clustered mailbox server cannot co-exist with any other server role.

Choose “Single Copy Cluster” as the cluster type, give the cluster a name, and specify a path for the database files.  The database path must be on a shared cluster disk.

Finally, give the cluster an IP address.

Exchange setup will configure all of the required cluster groups and resources for the underlying failover cluster automatically.  Once the active node is installed repeat the setup process on the passive cluster node, this time choosing “Passive Clustered Mailbox Role”.

Managing a Single Copy Cluster

For most Exchange administrative tasks the clustered mailbox server will appear like any other mailbox server.  For example, the storage group will show up as with any other mailbox server.

[PS] C:>Get-StorageGroup

Name                      Server            Replicated
----                      ------            ----------

First Storage Group       EXCHMAILBOX       None
Second Storage Group      EXCHMAILBOX       None
First Storage Group       EXCHCMS           None

You can view the status of the CMS using the Exchange Management Shell.

[PS] C:>Get-ClusteredMailboxServerStatus

Identity                        : EXCHCMS
ClusteredMailboxServerName      : EXCHCMS.contoso.com
State                           : Online
OperationalMachines             : {EXCHMAILBOX1 <Active,...
FailedResources                 : {}
OperationalReplicationHostNames : {exchmailbox1, exchmail...
FailedReplicationHostNames      : {}
InUseReplicationHostNames       : {exchmailbox1, exchmail...
IsValid                         : True
ObjectState                     : Unchanged

Although the CMS is configured as part of the Microsoft Cluster Service it should not be administered using Cluster Admin (cluadmin.exe).  Instead, Exchange cluster operations such as moving the cluster group to another node should be performed in the Exchange Management Shell.

[PS] C:>Move-ClusteredMailboxServer
cmdlet Move-ClusteredMailboxServer at command pipeline
position 1

Supply values for the following parameters:
Identity: exchcms
TargetMachine: exchmailbox2
MoveComment: Testing

Confirm
Are you sure you want to perform this action?
Moving clustered mailbox server "exchcms" to target
node "exchmailbox2" with move comment "Testing".

[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend
[?] Help  (default is "Y"):y

Cluster Continuous Replication

In the next part of this series I will demonstrate Cluster Continuous Replication for Exchange Server 2007.