In the 1960s, computer makers began placing spools of miniature magnetic tape into hard plastic cartridges. These cartridges were more durable, portable, and convenient than the larger open reels of magnetic tape, and their popularity as a backup medium for ever-growing hard disks increased in the 1970s and 1980s. Like earlier open-reel systems, the capacity of tape-cartridge systems had the advantage of flexible capacity. When storage needs increased, tape manufacturers simply created cartridges that held more tape. More tape meant more space.
Today, tape cartridges like the 800GB LTO Ultrium (lower left) remain in use for large-scale server backups, though their popularity has diminished over the last decade as hard-drive-to-hard-drive transfers have gained favor.