any hard drive can obviously be removed, the term
hard disk drive refers to hard drives designed to be
removed and reinstalled easily, without opening the case or
disconnecting and reconnecting cables. There are two distinct types
of removable hard disk drives:
Most such drives, including the Iomega Jaz and Castlewood ORB, use a self-contained, sealed cartridge about the size of a thick 3.5” floppy disk. The cartridge contains only the disk itself. The head mechanism resides in the drive. You insert the disk into the drive much as you would a floppy disk. Inserting the disk causes a shutter on the disk to open, allowing the drive’s head mechanism to read and write the disk. The Iomega Peerless system instead uses a cartridge that amounts to the HDA (head-disk assembly) of a standard hard drive. Cartridge-based units are available in internal and external versions, using IDE, parallel port, SCSI, USB, PC Card, or FireWire interfaces.
These drives are actually just modified drive bays that allow a standard hard drive mounted in a carrier assembly to be inserted and removed easily. The frame resides permanently in an external drive bay, and is connected permanently to power and to the IDE interface or SCSI host adapter. The carrier assembly contains power and data cables, which remain permanently attached to the hard drive. The rear of the carrier assembly contains a custom ...