DASD, pronounced DAZ-dee (Direct access storage device), is a general term for magnetic disk storage devices. The term has historically been used in the mainframe and minicomputer (mid-range computer) environments and is sometimes used to refer to hard disk drives for personal computers.

What is the difference between DASD and tape?

A record on a DASD can be accessed without having to read through intervening records from the current location, whereas reading anything other than the "next" record on tape requires skipping over intervening records, and requires a proportionally long time to access a distant point in a medium.

What is a DASD volume?

DASD volumes are used for storing data and executable programs (including the operating system itself), and for temporary working storage. ... A data set can be located by device type, volume serial number, and data set name. This structure is unlike the file tree of a UNIX® system.