website redundancy

hi there
anyone knows of a way i can implement a site to be served from more than one physical machine. ie if one server goes down another one will automatically take over serving that site.

i am thinking of two ways this can be achieved :
1) if the IP that the domain points to can somehow be changed to a different IP whenever a particular IP cannot be resolved. But i dont think most DNS servers in use supports anything like that.
2) if the hardware address gets modified dynamically when an iP cannot be resolved...

the idea of placing an intermediary server in the middle wouldnt really work since the intermediary server itself might go down and the site would go down with it.

any ideas/links to this would be appreciated.

thanks

nayeem

I'm not sure but I think you need some sort of cluster such as Beowolf. Try another forum too.

read the "High availability FAQ" (it came with my SuSE distro...) - they have very interesting stuff like connecting two scsi controllers from two different machines to one cable with the drives also on them (for immediate take-over if the other machine fails).
And iirc they have scripts to connect 2 PCs via serial line and if one fails to send the "heartbeat" signal every 3 seconds, the other will setup its NIC to take over IP AND ARP addresses and continue the task until the other machine is back up.

Sort of like a local mini 'Disaster Recovery' system!

Heh cool stuff to read up on