Storage area network (SAN)
A network which is created by attaching storage devices such as disk arrays and tapes to a common server so that the storage devices appear to be confined to operating system is known as storage area network.
How SAN Works
Data in SAN (Storage Area Network) can be stored using two basic modules as DAS (Direct Attached Storage) and NAS (Network Attached Storage). DAS is so named because it is a directly attached to a server without any intermediary network involved. Main distinguishing character of DAS (Direct Attached Storage) is its direct connectivity through a host bus adapter without the use of the networking devices as hubs, bridges and switches. In a network attached storage system, many independent clients can access the storage memory. The aim of the NAS (Network Attached Storage) is to provide only file based storage devices. DAS (Direct Attached Storage) can also provide multiple and parallel access if we equip this network with multiple ports. In the same way we can convert NAS (Network Attached Storage) to a DAS (Direct Attached Storage) by disconnecting the entire network and attach the port to a single computer. DAS (Direct Attached Storage) can be termed as an inefficient network because it cannot share its idle resources with other units in the network. DAS (Direct Attached Storage) and SAN (Storage Area Network) can overcome this deficiency but both these networks are costly and difficult to handle. Main DAS (Direct Attached Storage) protocols are SATA, SAS and fiber channel.