In: Root » Computers and technology » Storage Devices
First on the market was the ZipDisk, developed by Iomega Corporation. Although initially a proprietary system, Iomega has licensed Zip to other companies. Both drives and media are now available from multiple sources. As you might expect, Zip can be seen as an outgrowth of Floptical technology, but Iomega put the capacity and speed of Zip more in the range of small hard disks. The Zip medium uses an optically read servo track to allow repeatable head positioning in fine increments, fine enough to allow for a scant 100MB per disk cartridge. Each cartridge holds exactly 100,431,872 bytes, which is a true 95.8MB. The same ZipDisk drives work with nominal 25MB cartridges which hold 25,107,968 actual bytes. Because of the laser/mechanical formatting of the disks, low capacity ZipDisks cannot be reformatted to higher capacity. In fact, the servo tracks cannot be erased by any means that would not destroy the cartridge. The shell of the ZipDisk makes it a true cartridge. To achieve speeds in the hard disk range, the medium must spin at a high rate, and the friction from rubbing against a liner is anathema to speed. The thicker cartridge gives the ZipDisk spinning room and enables it to rotate at 2968 RPM. In addition, the ZipDisk drive has hard disk-like access speeds, with the first generation of drives having a 26 millisecond average access time. The disk requires about three seconds to spin up to speed or spin down, which becomes a factor only when exchanging cartridges. The actual Zip media disk inside a cartridge measures a true 3.5 inches across. Consequently, the cartridge must be larger than conventional 3.5-inch floppies and MO cartridges, measuring 3.7 inches (94 millimeters) square and a quarter-inch (6.35 millimeters) thick. These dimensions alone make the ZipDisk incompatible with traditional floppy disks. ZipDisk drives read only ZipDisks. Products using any of three interfaces-IDE, Parallel Port, and SCSI-are available. Current generation drives operate only as slaves or with identifications which do not allow booting PCs. The interface used by the drive dramatically affects performance. The SCSI drives can transfer information about three times faster than parallel-interfaced models. In any case, the actual throughput of the drive system is throttled by the rate at which the media is read, 1.4 megabytes per second. Instead of using a mechanical write protect mechanism on the cartridge shell, ZipDisks are write-protected electronically. The Iomega system provides three protection modes with optional password access limits as part of its ZipTools software. The three modes include conventional write protection that prevents the inadvertent alteration of data on the disk; read/write protection, which requires a password to access data on the disk; and unprotect until eject, which lets you work with the data on the disk but protects the disk when you remove it from the drive. The same software that adds write protection is required to remove it. Passwords, however, are not recoverable-even by Iomega.
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