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Direct-attached storage (DAS) refers to a digital storage system directly attached to a server or workstation, without a storage network in between. It is a retronym, mainly used to differentiate non-networked storage from the concepts of storage area network (SAN) and network-attached storage (NAS).
A typical DAS system is made of a data storage device (for example enclosures holding a number of hard disk drives) connected directly to a computer through a host bus adapter (HBA). Between those two points there is no network device (like hub, switch, or router), and this is the main characteristic of DAS.
Storage features common to SAN, DAS and NAS
Most functions found in modern storage do not depend on whether the storage is attached directly to servers (DAS), or via a network (SAN and NAS).
DAS has been referred to as “Islands of Information”. The disadvantages of DAS include its inability to independently share data or unused resources with other servers. Both NAS (network-attached storage) and SAN (storage area network) architectures attempt to address this, but introduce some new issues as well, such as higher initial cost, manageability, security, and contention for resources.
- Storage area network
- Network-attached storage
- Storage Management Initiative Specification
- Storage Networking Industry Association
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- "SAN vs. DAS: A Cost Analysis of Storage in the Enterprise". A Cost Analysis of Storage in the Enterprise. Capitalhead.com. 2008-11-03. Retrieved 2009-06-11.