As a result of these advantages of fibre channel, storage infrastructures can now be designed that provide:
Greater consolidation.
Better utilization of storage assets (disk and tape).
Ability to access any storage system from any host.
It is important to note that while fibre channel enables these types of networked architectures, it is a technology based on channel I/0. That is, each host virtually has its own dedicated storage; it just happens that storage may be in multiple systems or even in another building.
Network Attached Storage
Network attached storage leverages the maturity and universality of IP networks to provide access to information. Where SANs essentially provide network topologies to do block-level SCSI I/O, NAS provides network access to files. In order to accomplish this over IP, specialized file-serving protocols such as NFS (for Unix) and CIFS (for NT) are used by the hosts/servers to communicate with a file server. The file server itself actually manages and accesses the information and distributes it over the network to the initiating host. When you access a network drive through your workstation (eg. a 'G' drive on Windows), you are using network attached storage where the file server is some network server that you have been given access to through your network login.
Because the file server provides a centralized point of management for the file system that holds the files to be accessed over the network, the same exact file could be accessed by any of the hosts or clients logged into the file server. This makes network attached storage ideal for applications and environments that require the sharing of files among multiple hosts or clients even if they each have different operating systems. On the other hand, IP and Ethernet networks do not provide the same predictability of performance through a dedicated like service that channel based technologies like SCSI or fibre channel are designed to do. As a result, NAS is less well suited to those applications and environments that count on dedicated access to storage (eg. databases or client-server applications).