Exchange 2007 ushers in a brand new platform for Microsoft’s Messaging and Collaboration tool set. While leveraging a great deal of the existing Exchange technology, Microsoft made major changes to the architecture and functionality of the Exchange system. Not the least of these was the introduction of three new replication tools; Local Continuous Replication (LCR), Cluster Continuous Replication (CCR) and Standby Continuous Replication (SCR).
Many Double-Take Software clients have been moving from earlier versions of Exchange Server to this new platform, and they’ve been asking us if Double-Take is still needed, given that replication is now built-in to the Server itself. The answer is usually “Yes!” This week we’ll look at why you would use Double-Take to protect Exchange 2007 in a simple configuration, one server that houses all Exchange roles.
In single-server Exchange 2007 environments, all systems that are needed for Exchange functions are housed on the same box. So creating another Exchange 2007 server in another site and then using SCR to keep a copy of the data on the second box seems to cover all the bases when it comes to Disaster Recovery (DR). However, scratching the surface of the solution raises a few issues that you’ll need to address.
First off, SCR will require very strict configurations of Exchange databases to work. Only one Store per Storage Group will limit your configurations, especially if you wanted to spread out your users over many Stores to aid in backup and administrative tasks. While Exchange 2007 permits up to 50 Storage Groups, you will also 50 sets of logs and data locations to manage.
SCR also limits the number of Public Folder databases to 1 per organization. That means that if you have more than one site with and Exchange server, and you want to use different Public Folder databases, you cannot use SCR to protect the Public Folders.
So, if you do not want to have only one Store per Storage Group, or if you have more than one Public Folder database, you still need a 3rd party tool, like Double-Take, to provide a total replication and failover solution. The benefit is that you also get automated failover (no PowerShell scripting required as with SCR) and more ease of use and flexibility overall with the options provided by the Double-Take Application Manager.
Finally, SCR does not contain integrated failback solutions to get back to the production server. Currently, move mailbox operations are the only included strategy. DTAM allows for failback to the original server on the same hardware or new hardware if necessary.
As with any other Microsoft product, SCR absolutely has a place in any organization. However, it may not provide all of the flexibility and capability that you need when considering High Availability for Exchange Server 2007. Double-Take’s product line is a great addition to the new technologies introduced in this new version of Exchange.
Next week… Multi-Server environments.
Filed under: Exchange, Product Information | Tagged: 2007, CCR, Double-Take, DTAM, Exchange, FFO, LCR, SCR
