We use the new dual processor Xserver from Apple Computer as our primary server platform. Its rack mounted and specifically design for the demands of a system that is online 24/7 - 365 days a year.
Our servers have mirrored internal hard drives to ensure uninterrupted operation in case of a hard drive failure. The server sees them as one hard drive, so if one goes bad, the server just keeps humming right along. We also have and external, bootable hard drive backup system in the remote chance that both internal hard drives go bad. The internal drives are automatically backed up to the external drive at midnight every night.
The server software is the industry standard Unix Apache Web Server software, the most used server software in the world. It's speed, flexibility and open source origins ensures it will be an improving standard for many years to come.
We also run several mail servers and mail list servers on separate platforms.
Our servers are all networked to a special system that
monitors the activity. If for any reason a server is
inaccessible for more than 4 minutes, the system will
automatically restart the server and it will be up and
running again in no time.
In case of a power failure, we have the server hooked into a battery backup.