Yes, its possible. There are new servers available with out-of-band access, where you can basically access the console remotely (without even bootup). I have yet to see any offer of such service though. Must be expensive.
Regarding backup, you'll have to make backup of each and every configuration file you have touched (you can leave the default ones). Plus you won't be able to do auto-magical restore either.
Usually your data files are in separate directories, so even if you have to do OS restore, you can just restore the data directories, a few important config files and be up asap.
There is a shell script for sun cobalt RaQ servers to perform backup from one machine to another through FTP. I do not know if it will work on a standard linux box but I think if directories tree are modified it will do the job.
Anyway, here is the link below to d/load the script and procedure is explained in details.