Direct access storage device definition

Direct access storage device

A direct access storage device (DASD) refers to any storage device that is capable of reading from and writing to specific locations within the storage medium directly. While DASDs generally include devices that are internally connected to the system such as HDDs and SSDs, sometimes external storage devices such as thumb drives can also be considered DASD.

Compared to sequential access storage devices where you need to go through all preceding data to get a particular piece of information, with DASD you can jump straight to the desired data without any delay.

See also: thumb drive

Direct access storage device benefits

Performance. Since the storage is directly connected, the performance is generally consistent.
Simplicity. DASDs are typically easier to configure and manage than networked storage solutions.
Cost-effective. Often, it is more affordable than advanced network storage solutions.
Security: The data remains localized, so the risks associated with data transfers across a network are mitigated.
Availability: Since DASDs are directly connected, they aren’t affected by network outages.

Direct access storage device drawbacks:

Scalability. Expanding the storage might mean physically adding new devices, which the system might not support, whereas expanding network storage may be easier.
Data sharing. Because DASDs are generally accessible by a single computer, sharing data across multiple devices can be difficult and largely depend on the device used.