We have one Unity Server running 4.2(1) and plan to upgrade to the latest version of 7. We also have a new Exhcnage 2007 server. Our current Unity is not intgrated with Exchange but we plan on integrating it during our upgrade. We do not have a new server but we bought hard drives to place in the server to perform the upgrade so if we run into problems and need to roll back we can easily do so by swapping the hard drives.
I have done some reading and some people suggest using COBRA and other suggest using DIRT. What is the difference between the two tools or what one should we use? Any other suggestions for our upgrade would be greatl appreciated.