Intelligent Peripheral Interface

Intelligent Peripheral Interface was a server-centric storage interface used in the 1980s and early 1990s with an ISO-9318 standard.

The general idea behind IPI was that the disk drives themselves are as simple as possible, containing only the lowest level control circuitry, while the IPI interface card encapsulated most of the disk control complexity. The IPI interface card, as a central point of control, was thus theoretically able to best coordinate accesses to the connected disks, as it "knew" more about the states of the connected disks than would, say, a SCSI interface.

An IPI-2 bus could provide a data transfer rate in the vicinity of 6 MB/s.

In practice, the theoretical advantages of IPI over SCSI were often not realized, as they only materialized when around 5 to 7 disks were connected to the interface, which was by that point saturated.

IPI systems were often shipped by Sun Microsystems on original sun4 architechture 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.