Network-Attached Storage

• A network-attached storage (NAS) device is a special-purpose storage system that is accessed remotely over a data network (see Fig. 12.6).

  Figure 12.6: Network-attached storage.

  
• Clients access network-attached storage via a remote-procedure-call interface such as NFS for UNIX systems or CIFS for Windows machines.
• The remote procedure calls (RPCs) are carried via TCP or UDP over an IP network -usually the same local-area network (LAN) that carries all data traffic to the clients.
• Network-attached storage provides a convenient way for all the computers on a LAN to share a pool of storage with the same ease of naming and access enjoyed with local host-attached storage. However, it tends to be less efficient and have lower performance than some direct-attached storage options.
• ISCSI is the latest network-attached storage protocol. In essence, it uses the IP network protocol to carry the SCSI protocol.
• Thus, networks rather than SCSI cables can be used as the interconnects between hosts and their storage. As a result, hosts can treat their storage as if it were directly attached, but the storage can be distant from the host.