17 Facts About SCSI

The SCSI standards define commands, protocols, electrical, optical and logical interfaces.

The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.

The initial Parallel SCSI was most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices.

SCSI is derived from "SASI", the "Shugart Associates System Interface", developed beginning 1979 and publicly disclosed in 1981.

Since its standardization in 1986, SCSI has been commonly used in the Amiga, Atari, Apple Macintosh and Sun Microsystems computer lines and PC server systems.

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SCSI has never been popular in the low-priced IBM PC world, owing to the lower cost and adequate performance of ATA hard disk standard.

Serial interfaces have a number of advantages over parallel SCSI, including higher data rates, simplified cabling, longer reach, improved fault isolation and full-duplex capability.

Therefore, iSCSI uses logical connections instead of physical links and can run on top of any network supporting IP.

SCSI is popular on high-performance workstations, servers, and storage appliances.

Since 2005, SPI was gradually replaced by Serial Attached SCSI, which uses a serial design but retains other aspects of the technology.

SCSI interfaces have often been included on computers from various manufacturers for use under Microsoft Windows, classic Mac OS, Unix, Commodore Amiga and Linux operating systems, either implemented on the motherboard or by the means of plug-in adaptors.

Parallel SCSI specifications include several synchronous transfer modes for the parallel cable, and an asynchronous mode.

Internal parallel SCSI cables are usually ribbons, with two or more 50–, 68–, or 80–pin connectors attached.

ISCSI usually uses Ethernet connectors and cables as its physical transport, but can run over any physical transport capable of transporting IP.

SCSI RDMA Protocol is a protocol that specifies how to transport SCSI commands over a reliable RDMA connection.

Each device on the SCSI bus is assigned a unique SCSI identification number or ID.

In modern SCSI transport protocols, there is an automated process for the "discovery" of the IDs.