Not necessarily - the disks should be in a RAID array. Depending on how the servers are setup, you can loose multiple disks without losing a server. Some of the newer SAN (storage area network) technology like the HP EVA and XP kit (as one example) can lose an entire controller, fabric switch, shelf or multiple disks without going down, and can also write your data to a different SAN on the fly (technology is called Continuous Access) - so if the whole SAN goes down , you are not necessarily stuffed (depending obviously on the state of the shutdown). You can also have multiple HBAs (Host Bus Adapters) in your server, so if you lose one adapter or a PCI slot, its as if nothing has happened...
Back on topic - Note on this Google Accelerator :
Yugh! I wont touch it for the following reasons :
1. It slows down access to local sites. It has to go all the way to the US servers everytime you hit a local web site.
2. Google will be keeping record of web sites you are visiting, albeit anonymously (so they say).
3. It breaks corporate configuration scripts.
4. I dont see it being any better at caching web sites compared to what Firefox already does.