What surprises me most is that something as simple as a Faraday's
Cage (I hope it is called approximately the same in English) is often
not used to protect servers. Over here we had a series of cases
where lightnings caused serious damage to servers, one of my fa-
vourite forums was down for weeks and lost more than a month of
content because server and backup where in the same building and
not protected against lightning.
For lightning protection, a Faraday Cage is often overkill; instead, good lightning rods (ground rods) and surge suppressors on the power source are deemed normally adequate for such protection - and have generally proved to be adequate when flash came to bang.
Couple surge protection as above with off-line and off-site backups, and you really should be able to handle most crashes quickly and efficiently, with the acquisition of replacement hardware being potentially the most delay-causing factor in resurrecting a data center.