A storage area network (SAN) is the step-up of a Direct Attached Storage, in which the storage capacity in the network is allocated to a server. This allocation takes place dynamically, so that the memory could also be allocated to other servers flexibly and with little administrative effort. The SAN-compatible hard disk arrays support this function or it is implemented directly. SANs enable multiple servers with multiple storage systems to be connected in a network, even over long distances. The structure of a SAN corresponds to a local area network: routers, hubs and switches are also used here.