I am on GPL version and have got fully tuned and perfectly working Centos server with Virtualmin/Webmin on it. Is it possible (is there a solution, maybe built-in feature I don't know about in this product?) to have another one (I mean server) - just for backup purposes or to increase stability (like "one server is down, the other one is still running" with the exact same content). What is the best solution here - by making scheduled backups (settings, domains, full filesystem?) to each other's ftp every night or so? Then if the one is down - the other one can be simply restored manually from the files and settings uploaded. Thanks.
I don't believe there's any one recommended way of handling that, as of today.
Certainly, making backups to a remote machine and restoring them is one way of handling it. The thing about this is that it's trivially easy to setup.
But there's also rsync, drdb, heartbeat, mysqlhotcopy, and numerous other tools which used by themselves or in conjunction can do some interesting things.
It even sounds like at some point in the future, Virtualmin may support a hot backup, of sorts.
There's some good discussion that took place here:
http://www.virtualmin.com/forums/limit/10/limitstart/0/general-discussio...
I'd enjoy hearing about what you end up going with, feel free to post back any solutions you put together.
-Eric