Direct-Attached Storage (DAS)
DAS is the most basic level of storage, in which storage devices are part of the host computer; as with drives, or directly connected to a single server, as with RAID arrays or tape libraries.
In order for clients on the network to access the storage device in the DAS model, they must be able to access the server it is connected to. If the server is down or experiencing problems, it will have a direct impact on users' ability to store and access data.
DAS is ideal for localized file sharing in environments with a single server or a few servers – for example, small businesses or departments and workgroups that do not need to share information over long distances or across an enterprise. Small companies traditionally utilize DAS for file serving and e-mail.