What is "sgpio"

Serial General Purpose Input/Output (SGPIO) is a four-signal (or four-wire) bus used between a host bus adapter (HBA) and a backplane. Of the four signals, three are driven by the HBA and one by the backplane. Typically, the HBA is a storage controller located inside a server, desktop, rack or workstation computer that interfaces with hard disk drives (HDDs) to store and retrieve data. It is considered an extension of the general-purpose input/output (GPIO) concept.

The SGPIO specification is maintained by the Small Form Factor committee in the SFF-8485 standard. The International Blinking Pattern Interpretation indicates how SGPIO signals are interpreted into blinking light-emitting diodes (LEDs) on disk arrays and storage backplanes.