One solution that I've become particularly fond of because of its capabilities, richness and features is the replication solution InMage Systems Inc.. It has a very lightweight I/O tap agent that goes on a virtual desk and can replicate data to an appliance at a local site. This reduces the amount of data that is sent across a WAN but still captures all of the replicated data at the host level.
So you have very good data integrity but very low I/O overhead going onto a virtual desk. One of the challenges with agent-based replication solutions has always been the I/O load that it places on the virtual desk, but also the management overhead that it creates in the environment. InMage's solution is very low on I/O impact but still harvests the benefits of agent-based replication. The benefits of agent-based replication include better data integrity because the agent can understand what is going on at the host.
If you have Exchange on that host, an agent can usually recognize when you asses the host and have taken a snapshot. So it knows you have a usable server at that point in time versus an array-based replication tool that is just replicating data and can't tell you whether that server image is usable at any point in time. If you corrupt it, or there is a disaster that corrupts it, that data may get replicated as well.
InMage has a very interesting solution for replicating at the host level that is very lightweight and captures points in time where data is good. Because it consolidates all the streams from multiple guests to the site and it replicates that over a WAN so you don't get as much data change going on as you do when you're replicating a whole bunch of different streams.
That's one solution, but others exist as well, from vendors like SteelEye Technology Inc. And then if you're dealing with sticky issues around moving physical servers to virtual images, there are vendors out there like Racemi Inc., Platespin (which has been acquired by Novell), IBM Corp. and VMware Inc. with their P2V solutions. So there are some interesting possibilities for doing that hybrid physical environment to virtual environment at a remote site.
This was first published in September 2008