.... At this time, only governments are willing to part with the required cash to build systems meeting six nines (99.9999%, <0.53 minutes annual downtime), or better (NASA, NORAD, US Space Command, etc). Usually, this is done using multiple site redundancy.
Hosts meeting three nines, or better, typically have redundant power supplies and integrated UPS, bootable RAID for the OS, redundant NICs, and SMP CPU configurations.
um...is an smp cpu configuration really going to help your uptime? or are there operating systems or hardware out there that can say to themselves "hmph! cpu 2 seems not to be working correctly...i'd better spin it down." just for fun a few years back i decided to check if the sun e4000 we had had hot-swappable cpus (i figured it didn't, but why not try it?) and i pulled one of the boards. it didn't like it too much. -- |-----< "CODE WARRIOR" >-----| codewarrior@daemon.org * "ah! i see you have the internet twofsonet@graffiti.com (Andrew Brown) that goes *ping*!" andrew@crossbar.com * "information is power -- share the wealth."