DAS: Still Useful After All These Years


In the nascent days of corporate computing, there was only one kind of storage configuration—hard drives within workstations and servers or hard drives in enclosures that were directly connected to workstations and servers. Being the only storage architecture, this approach did not warrant a name. But networks and applications grew larger and more complex, and network-attached storage (NAS) and storage area networks (SANs) emerged to meet the needs. These advances in storage prompted the initial configuration to be named—direct-attached storage (DAS). NAS allows multiple devices across a network to access a storage platform and SANs provide multiple networked devices with block-level access to multiple storage platforms. Both have proven very useful in enterprise networks, but DAS can still play an important role for organizations.

DAS can offer some performance benefits because the server does not need to cross the network for reads and writes. This makes DAS useful for supporting demanding applications like Microsoft Exchange, audio and video streaming, digital video recording, and media servers. Another advantage is DAS is much simpler to deploy and maintain than NAS or SANs. NAS and SANs require network planning and the acquisition and installation of gear like switches, routers, cabling, and connections. By avoiding these costs and complexities, DAS remains a viable choice for small businesses or for branch offices where only one physical server is deployed.

A knock on DAS is its limited scalability, but using a RAID array for the storage platform can deliver substantial storage capacity. Well-engineered RAID solutions offer much of the fault tolerance, availability, and data protection provided by NAS and SANs with such features as disk, controller, and cooling redundancy. Moreover, they allow JBODs to be connected to them, greatly increasing capacity. The bottom line is when storage does not need to be shared or virtualized, DAS, particularly when anchored by RAID platforms, offers a cost-effective solution that is easy to own and manage.