RK02 and RK03 are removable magnetic storage disk drives with moving heads, which were marketed by DEC (Digital Equipment Corporation) but designed and manufactured by Diablo Systems, a company later acquired by Xerox. They were inspired by IBM 2315 removable disk drive. The disk drives were used in the DEC PDP family of minicomputers and, together with the disk controller and the DECpack cartridges, they formed a complete mass storage system, able to offer a cost-effective solution for the storing of large volumes of random access data.
Insights - Fun facts
The original RK02 (Diablo Model 30) was soon joined by RK03 (Diablo Model 31), a double-density model able to hold twice as much data (600000 words against 1200000 words).
Like the other cartridges used in contemporary removable disk drives, DECpack cartridges held a plate with a 14-inch(35.56 cm) diameter coated with iron oxide. The read and write heads were contained within the hard drive. The above mentioned plate was set in a pressurized protective case, which had to be fully inserted into the drive. This controlled the disk opening and extraction, in order to prevent dust and other debris from damaging either the drive or its reading heads.
Since these drives used low level pre-formatted disk cartridges, it was necessary to use different cartridges depending on the chosen system. For example, the cartridges used in DEC PDP-8 minicomputers where physically incompatible with the ones used in DEC PDP-11, although their disk drives were perfectly identical .
RK02 and RK03 units were later replaced by RK05 disk drive - directly manufactured by DEC - which used the same cartridges.
Bibliography
Computer History Wiki: https://gunkies.org/wiki/RK02_disk_drive
Wikipedia: https://en.wikipedia.org/wiki/RK05
