Another trendy buzzword in data storage is SAN, or storage area network. A SAN is nothing more than one or more hard drives able to be shared among several computers, generally via high-speed FireWire, Fibre Channel, or SCSI connections (without using a conventional Ethernet-based network). NAS, or network attached storage, typically refers to one or more hard drives with their own Ethernet (or wireless) interfaces, sort of minimalist file servers. (Increasingly, they're simply called "network drives.") In other words, SAN and NAS equipment may be nearly identical, except for their interfaces.
Your office may have a SAN or NAS system available, and if enough adequate free space is available to you, there's nothing wrong with using either for backups. However, I would not buy SAN or NAS products primarily for home or small-office backup use. When it comes to backups, they provide little or no benefit over conventional FireWire or USB hard drives. And because they can't run backup software themselves, you still have to set up a backup serveror have each machine run its own backup application.
Also, bear in mind that it may not be possible to boot your machine directly from a duplicate stored on a SAN or NAS device; in general, you will have to restore (or re-duplicate) a duplicate to another hard drive first. And although some SAN or NAS setups may offer terrific speed and capacity for frequent backups, transporting a set of media off-site (or back when a restore is needed) is likely to be difficult or impossible.