Buying a DR solution without taking a long, hard look at the associated networking requirements is a bit like buying a house without pausing to consider whether it meets your basic needs or what you’re likely to end up paying to heat and cool the place. That’s because, long after the DR solution itself has been purchased, you’ll still be paying the freight on the network traffic that the system generates day after day after day.

The thing to remember is this: most existing DR solutions were not designed for the Exchange environment. So once you’re confronted with replicating Exchange over the WAN, it quickly becomes apparent that these traditional architectures are actually major bandwidth hogs.

The reason is pretty easy to understand—virtually all file and block solutions replicate each Exchange transaction at least twice. So, as a consequence, every email message, every calendar entry, every contact change and each and every other thing that happens on the primary Exchange server ends up triggering at least twice as much activity across the WAN. In the aggregate, you can well believe this adds up to some serious network volume.

Oh, and if you happen to have a policy that limits the number of days that email can be stored on the server, things are sure to get even more interesting once that limit is reached since the system will then attempt to replicate the whole .edb file over the network. Additional problems will arise for block-level replication solutions whenever you perform white-space compression on your primary Exchange servers. And you just know that’s not going to be pretty.

MailShadow®, on the other hand, works in a variety of ways to reduce the WAN overhead associated with the traffic that passes between your primary Exchange servers and your recovery servers. First and foremost, MailShadow transmits transactions only once—passing along only that information which is specific to the transactions and, even at that, only to the select number of mailboxes that you’ve chosen to replicate.

What’s more, MailShadow’s proprietary transport protocol uses buffering, packet recombination and compression to ensure high throughput even over high-latency lines. Just the resulting savings in WAN bandwidth alone, repeated from one month to the next, means that MailShadow can end up more than paying for itself in short order.