Direct-attached storage

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.

The main protocols used for DAS connections are Parallel ATA, SATA, eSATA,[1] NVMe, Parallel SCSI, SAS, USB, and IEEE 1394.

DAS is typically considered much faster than NAS due to lower latency in the type of host connection although contemporary network and direct connection throughput typically exceeds the raw read/write performance of the storage units themselves.

A SAN (storage area network) has more in common with a DAS than a NAS with the key difference being that DAS is a 1:1 relationship between storage and host whereas SAN is many to many.