Intelligent Peripheral Interface
The idea behind IPI is that the disk drives themselves are as simple as possible, containing only the lowest level control circuitry, while the IPI interface card encapsulates most of the disk control complexity. The IPI interface card, as a central point of control, is thus theoretically able to best coordinate accesses to the connected disks, as it "knows" more about the states of the connected disks than would, say, a SCSI interface.
In practice, the theoretical advantages of IPI over SCSI were often not realized, as they only materialized when several disks were connected to the interface, which could then easily become a bandwidth bottleneck.
IPI systems were often shipped by Sun Microsystems on original sun4 architecture servers, but the above limitation and reliability problems made them unpopular with customers, and the technology basically disappeared by the second half of the 1990s.
- Allan, Dal, ed. (1988), ISO/DIS 9318 -- Information Processing Systems -- Intelligent Peripheral Interface, International Organization for Standardization