Review: Low-Cost Server Mirroring

Not long ago, solution provider AppTech found itself recovering data and e-mail from two separate server hardware crashes at two unrelated companies. Both of these firms experienced significant downtime. As a result of the downtime and subsequent loss in revenues, AppTech was tasked by each firm with creating a solution that would eliminate any downtime.

The solution needed to be compatible with Microsoft Windows Server 2003 Standard Edition, affordable and easy to implement. It also needed to guarantee 100 percent uptime. Engineers first looked into Distributed Files Services (DFS) and clustering, but they proved to be too expensive with too many fail points. Engineers just didn't feel comfortable with all of the requirements and the fact that there was no real assurance of achieving 100 percent uptime.

During conversations with Microsoft support engineers, they let slip they had used Double-Take for Windows server mirroring software to accomplish what AppTech engineers were looking to achieve. As a result, AppTech brought the software into its lab for testing.

Double-Take provides high availability and failover in case of a server-down situation. It's a great alternative to Microsoft's Cluster Service because it's less expensive and much easier to install for smaller businesses that can't afford or maintain a server cluster. Licenses cost $2,995 for each server in the mirror. Double-Take claims it's as easy as installing antivirus on your server. AppTech engineers would not go so far as to say that, but the documentation is thorough and easy to follow.

AppTech first installed the software in a test lab with two Dell PowerEdge 2300 servers. Engineers mirrored Windows Server 2003 Standard R2 SP1 as a file server with Microsoft Exchange 2003 SP2. The setup and installation of the Double-Take software was accomplished with two separate applications from Double-Take: one for the file server and one for Exchange/SQL.

Once the application to mirror Exchange was finished, it can never be used again. The application to mirror the file server also configures and monitors the mirror and manages failover. Again, the documentation is easy to follow for both installations individually, but it is somewhat complicated when mirroring more than one network service on one server (Exchange, File Server or SQL). Double-Take should integrate both these installations into one simple application.

Once engineers completed installation, they created test data and messages. The mirror of both the file server and Exchange worked flawlessly. After engineers were satisfied that the mirror worked, they created a server-down scenario, which showed how the system would then fail over to the second server.

During the failover process, the monitor detects if the server is down and requires the user to decide to fail over manually, which can be set up to automatically fail over as well. After failover, the second server assumes the identity of the original server without any problems at all. As for the clients, AppTech engineers either had to clear the ARP cache or simply restart the client. Once the clients were restarted, engineers were able to continue working with the network shares and Exchange as if nothing happened.

Next: The Bottom Line