The Helios II is a floppy disk drive unit system which uses a unique recording technique known as "firm" sectoring. Under optimum conditions each diskette can store 384,000 bytes of information.
That's over 3/4 million bytes on line with each Helios dual drive. Firm sectoring also allows faster data access and variable block sizes.
Up to four dual drives (8 diskettes) can be accessed by the system, so that over 3,000,000 bytes of data are online.
See also: Sol-20 Terminal Computer