Directly Attached Storage (DAS)

Direct Attached Storage (DAS) may be a dedicated digital storage device attached directly to the computer accessing it, as critical storage accessed over a computer network (i.e. network-attached storage). Advanced Technology Attachment (ATA), Serial Advanced Technology Attachment (SATA), eSATA, Small Computer System Interface (SCSI), Serial Attached SCSI (SAS), and Fibre Channel is the main protocols used for DAS connections. Examples of DAS include hard drives, solid-state drives, optical disc drives, and storage on external drives. The name “DAS” is a retronym to contrast with the storage area network (SAN) and network-attached storage (NAS).

In other words, DAS isn’t part of a storage network. The most familiar example of DAS is the internal hard drive in a laptop or desktop PC. In practice, the phrase direct-attached storage is used most often in reference to dedicated storage arrays attached directly to servers. It is used to distinguish DAS from networked storage arrangements, like SAN or NAS devices.

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 a hub, switch, or router), and this is the main characteristic of DAS.

The main protocols used for DAS connections are ATA, SATA, eSATA, NVMe, SCSI, SAS, USB, USB 3.0, and IEEE 1394.

A typical DAS device may be an internal or external hard disk drive. Depending on data criticality, disk drives may be protected with different levels of Redundant Array of Independent (or Inexpensive) Disks (RAID). Modern DAS systems include integrated disk array controllers with advanced functionalities.

The primary benefits of DAS include simplicity and low cost. Installing networked storage systems, like NAS and SAN devices, requires more planning, additionally because of the purchase and deployment of network hardware, like routers and switches, additionally to appropriate cabling and connections. Against this, most PCs and lots of servers include DAS already installed, and if we wish to feature more direct-attached storage, generally all we want to buy may be a storage device and possibly a cable. Maintaining DAS is additionally very simple; against this, SAN and NAS solutions usually require management software and should require monitoring software in addition.

DAS advantages include:

  • High availability.
  • High access rate due to Storage Area Network (SAN) absence.
  • Elimination of network setup complications.
  • Storage capacity expansion.
  • Data security and fault tolerance.

DAS drawbacks include:

  • Data not accessible by diverse user groups.
  • Allows only one user at a time.
  • High administrative costs.

DAS is additionally included in many servers. Connecting additional DAS devices to servers could be a little more complicated than adding DAS to a PC, but it’s generally simpler than connecting SAN or NAS devices because it doesn’t require us to style a network or purchase hardware like routers and switches. Counting on the kind of server, we are also able to add DAS within the style of additional drives in your existing server chassis. Other times, DAS sits during a separate chassis. We are able to also purchase DAS as storage appliances that we will connect on to our servers. DAS deployment may require some configuration, but most IT workers can handle it on their own without outside consultants or specialized technical experts.


Information Sources:

  3. wikipedia