Competitive Environments The Competitive Environment for Storage Area Networking Until the late 1990s, external data storage was entirely DAS, or directly attached storage, that is, storage attached directly to an application server. Even today, more than half of all external storage is DAS. Increasingly, storage is moving toward being attached through a network, either as NAS (network attached storage) a file-based system connected to application servers through a LAN, or SAN (storage area network) a block-based system connecting application servers to storage through a high-speed dedicated network using switches and hubs. More...