The term Direct Access
Storage Device (DASD) originated from IBM and referred to a peripheral magnetic drum storage device.Today the abbreviation DASD is generally used for external storage
devices that aredirectly connected to the server, whereby direct access to the storage always runs via the associated server. Free storage capacity
at one server is not accessible to applications at other servers. The term DASD is generally used for storage media with immediate access to the information, as opposed to storage media with sequential access. The first group of DASDs includes hard disks, floppy disks, DVDs, and RAID systems; the second group, sequential storage media, includes magnetic tapes on which the data is stored as linear blocks of data.