This title is a catchall for direct access magnetic media, which now includes solid-state drives (SSDs) and flash storage, in addition to just a bunch of disks (JBODs). In the old days, I/O performance was often increased by using faster disks or spreading the data across more disk actuators for concurrent access. For the record, the media used in online and other time-critical work are*
■Traditional hard disks (hard disk drives [HDDs]), introduced to the world via IBM’s RAMAC
■Solid-state drives (SSDs)
■Solid-state flash storage
■Magnetic tapes, normally now used for backup and restore
■Mass storage systems, such as the old IBM 3850 MSS†
■CDs, optical, floppy, stick, and other devices, used ...