Using a redundant backup server

[Eye for Video]

I have a client who requires a 100% uptime on his site. Something like a redundant backup server so if the main goes down, the backup can be on line very quickly. Since I don’t have my own servers, what advice would you give in looking for hosting service to provide this level of uptime? How do you describe and detail what’s involved with this? Any suggestions as to hosting companies so I can compare pricing?
Best wishes,
EfV

[aj_nsc]

ICDSoft.com has excellent uptime and, in my opinion, it's very competitively priced. The average uptime for all of its servers (there's quite a few is 99.990%)

Uptime of servers (https://www2.suresupport.com/network.php)
Pricing and hosting packages (http://www.icdsoft.com/hosting.php)