The Single Copy Cluster (SCC) is a high availability solution for the Mailbox Server role that has been vastly
improved with the creation of Exchange Server 2007. This clustered mailbox server, similar to that of an Exchange 2000/2003 active/passive cluster setup, provides service failover using a single copy of a storage group that is shared between the nodes.
Managing an Exchange 2007 Single Copy Cluster (SCC) setup
Part 1: A basic Single Copy Cluster setup in Exchange 2007
Part 2: Configuring Single Copy Cluster (SCC) nodes and shared cluster disks
Part 3: Creating a Windows Server 2003 cluster for an Exchange SCC setup
Part 4: Installing Exchange Server 2007 clustered mailbox roles on SCC nodes
Part 5: Verify Exchange 2007 clustered mailbox server functionality
Part 6: Exchange 2007 Single Copy Cluster-based setup review
A basic Single Copy Cluster setup in Exchange 2007
In addition to the CCR type of setup, Exchange 2007 supports the Single Copy Clusters (SCC) type, which, as mentioned in the beginning of the chapter, is more or less identical to the traditional active/passive clusters we know from previous versions of Exchange. This means that an SCC-based cluster only provides service failover and still has a single point of failure when it comes to the databases, unless a shared storage solution that provides redundancy in other means is used in the environment. An SCC-based cluster using a fault-tolerant SAN is just as good as a CCR-based cluster in terms of data availability, but such a solution is much more expensive than a CCR solution.
An SCC is basically a clustered mailbox server that consists of two or more servers (known as nodes) that share the same storage (for databases and log files). The shared storage subsystem is typically a SAN. In Figure 8.77 you can see what the architecture behind a typical SCC scenario looks like.
|Note: We know we mentioned it in the beginning of this chapter, but because it's important that you understand this concept, we repeat: Exchange Server 2007 no longer supports active/active clusters. Only active/passive clusters are supported in Exchange 2007.|
The primary benefit of an SCC is that it provides high availability of server resources because one node takes over should the active node be taken offline or fail for some reason. In addition, you can apply hotfixes, service packs, and the like to the nodes without having any downtime of your mission-critical mailbox servers. However, bear in mind that an SCC is susceptible to failure of the shared storage subsystem. This means that no matter how many nodes are part of your cluster, you'll always have a single point of failure when you're using SCC opposite a CCR-based cluster, which, as we demonstrated, provides storage group failover via the new log file shipping and replay functionality.
Since most of you don't have the necessary hardware for a cluster, before you actually decide to deploy one in your environment, we thought it would be a clever idea to show you how to install an SCC in a Virtual Server 2005 R2 environment. Pretty much all the steps in this section can be used to install the SCC on real hardware, too.
|Some Independent Advice: Some of you might wonder whether standby clusters are supported in Exchange 2007, just as they were in Exchange 2003. A standby cluster is a Windows cluster that matches a production Exchange cluster in terms of hardware and software configuration, including Windows and Exchange versions and any updates or hotfixes that have been applied. In addition, a standby cluster has the Exchange program files installed but has not yet been configured with any Exchange Virtual Servers (EVS). Lastly, a standby cluster can only be used when all Exchange Virtual Servers on the production cluster are offline.
So, is a standby cluster supported in Exchange 2007? The answer is no, but then it's really not that useful anymore, since Exchange 2007 gives us the ability to recover an Exchange 2007 cluster using the new Exsetup/RecoverCMS switch (which is similar to the /DisasterRecovery switch we know from previous versions of Exchange). Even better, the /RecoverCMS switch can be used to recover both Exchange 2007 CCR and SCC-based cluster setups. We'll take a closer look at the /RecoverCMS switch in Chapter 10.
To follow the steps throughout this section, you need the following:
- One physical machine running Virtual Server 2005 R2. Since this product is free to download from the Microsoft Web site, getting it shouldn't be a problem. Download Virtual Server 2005 R2.
- A Windows 2003 Active Directory forest with at least one domain controller (raised to 2000 or 2003 forest functional level).
- At least one existing Exchange 2007 Hub Transport/Client Access server already installed in the aforementioned forest.
- Two virtual guests running Windows 2003 R2 or Windows 2003 SP1 Enterprise Edition with at least 512MB RAM and two virtual NICs each -- one for the Public network and one for the Private network (the heartbeat network). This means that you need to create an additional virtual network on the virtual host server; None (Guest Only) is sufficient for this network.
|Note: To install an Exchange 2007 Single Copy Cluster, you also need to install the cluster hotfix mentioned in MS KB article 898790, which at the time of this writing can be requested by contacting Microsoft Product Support Services. Microsoft is working on making it public.|
Return to table of contents or proceed to part 2 on how to create quorum disks for an Exchange 2007 Single Copy Cluster.
|This chapter excerpt from How to Cheat at Configuring Exchange Server 2007: Including Outlook Web, Mobile, and Voice Access, by Henrik Walther, is printed with permission from Syngress, a division of Elsevier, Copyright 2007.
Click here for the chapter download.