+1 -- most of the comments are about minimizing downtime, which you should of course to do to the extent practical, but at some point, whether you're a one-employee company or not, if you have no internet access and your servers are down you have to keep calm and accept that there will be some downtime and it's not the end of the world. You may even be surprised how few customers notice anything went wrong (depending on the kind of service you're running).