Direct Attached Storage (DAS) is a term used to describe added storage devices (storage extensions) that are connected directly to a server or workstation. The term is used primarily to differentiate between this kind of storage mechanism and Network Attached Storage (NAS).

A DAS unit typically consists of an enclosure and one or more hard drives. While low end DAS systems rely on the directly-connected server’s controller, high end units are more likely to include a separate controller and provide features like fault tolerance and redundancy.