• United States
Neal Weinberg
Contributing writer, Foundry

Disaster recovery for Exchange servers, Part 1

Jun 01, 20043 mins
Enterprise Applications

* The Reviewmeister takes a look at WANSync HA Exchange

What happens when your Exchange server crashes? We wanted to find out, so we tested several products that claim to provide disaster recovery for Exchange e-mail servers.

Let’s start with our favorite product – WANSync HA Exchange.

WANSync HA Exchange is clearly built for an Exchange environment since it reads the Active Directory, the server registry and Exchange 2000/2003 files, and quickly gives an administrator a profile of where things are, how they’re set and options for synchronization intervals.

There are a number of ways to increase availability – increasing application platform support via power protection, for example, routing techniques and monitoring. Our tests, however, assume a site’s Exchange servers have become unavailable – gone from the network map entirely. This mandates Exchange services become available from an alternate site.

This disaster simulation was simple for us. We merely pulled the power feeding two servers, one of them running Exchange including an Active Directory Global Catalog server and the other a forest-partitioned server in the same Active Directory domain.

The real test was to find out whether products could sense the primary site was down, then recast the hotsite’s mirror to Exchange users. After the power failure we assessed how products detected the outage. We then wanted to see the products bring Exchange services back online by using our VPN connection to fail over operations to the secondary site. We tracked how many messages were lost during failover and clocked time to availability.

WANSync HA Exchange does this automatically. Of two available deployment options, we chose the high-availability one.

We linked the source and replication server by making the replication server a ‘switchover host’ and chose a replication name. The auto-discovery process in WANSync HA Exchange queried our Active Directory and each host for its information. It then offered appropriate default selections of items such as source host monitoring (heartbeat, timeouts, IP pinging, for example) and let us run scripts before switchover or switchback.

WANSync HA Exchange can redirect DNS to point to the failover Exchange server, then change it back if necessary at a failback point. Also, it can change the IP addresses so that the remaining live Exchange server can be found if DNS can’t (or shouldn’t) be changed. In both cases, users might have to exit Outlook or their mail readers, and flush their DNS cache as we had to do.

Of the four products tested, only WANSync HA Exchange prevented any outgoing messages from being lost at the time of failure. WANSync HA Exchange can auto-discover many Exchange facets such as file locations, Exchange specifics and logs. 

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