Multiple servers.

[JamesVaporH]

What your looking for is a replication server.

The replication server can be turned into a production server or a write only server (replication).

If for any reason the first server goes down then you can turn the replication server to production.

All the replication server will do is copy each and every change you make on the other server to the new one. But its not a easy task as it needs custom scripts.

You can also run a cluster server in which each server connects to each and it will work like a replicated server. But that is something i cannot explain as the documentation is needed since detail is better then just a summary.

 

[Whoo]

Most of the time you have 2 servers of each:

2 load balancers (1 active and 1 in standby mode) => this means you have one floating IP which routes to the active load balancer

eg:

load balancer 1: 192.168.0.1
load balancer 2: 192.168.0.2
floating IP: 192.168.0.3

All websites will point to the 192.168.0.3 which will then automatically switch (google for ucarp) to the active load balancer.

Mysql will be master/slave of which the slave can take over if the master may crash. Master/slave is still not 100% so if you get corrupt data on the master it will write it to the slave too causing you to have bad data on both servers :P

Ive read my stuff here: http://insanecoderz.org/359/server-administration/setting-fileserver-debianubuntu

 

[damoncloudflare]

CloudFlare Captcha

^^Thank you so much It's listed "always online" cache portion!

Sounds perfect.

EDIT: Wait, do users see captcha before entering the site?

No, not all users would see a captcha before they enter a site. The IP has had to show bad online activity from one of CloudFlare's data sources before a challenge happens (very few visitors actually see a challenge).