The hard disk industry has increased the capacity of non-removable disk drives every year. For removable storage, yearly increases are not desirable. It is more important to offer a capacity point that is usable for the desired applications and then hold that capacity point while increasing the installed base and lowering the price. CDs were designed to store more than 1 hour of music. Their capacity has been unchanged for 15 years. Floppy disks first increased in capacity from 0.25 to 0.5 to 1 MB, then stopped increasing. For text files, 1 MB was sufficient. Although improvements to 2 MB, 10 MB and then 40 MB have been offered over the last 10 years, none of them have been successful. Only recently, as the applications have shifted from text files to image files has there been an unmet need for higher capacity. Currently, there are several contenders to meet this need: super floppy disks at 100-200 MB, removable hard disks at 1 GB and erasable CDs at .65 GB.
For video disks, depending on the compression algorithms, 2 hours of HDTV will require somewhere around 15 GB. An erasable disk with a capacity of 30 GB or more would be able to record more than 4 hours with HDTV quality and more than 12 hours with standard definition TV quality. Industry representatives believe that these capacity points will be long-lived standards with wide acceptance for both consumer and computer applications. Both phase change and magneto-optic technology should be able to achieve capacities of 30 GB or more on a 12 cm disk.