What is SCSI?
SCSI (Small Computer System Interface) is a set of ANSI standards for connecting computer systems and devices. The vast majority of SCSI devices are used for data storage.
Although standard SCSI is a parallel technology, many serial SCSI variants exist, including FireWire and Fibre Channel.
SCSI is generally considered a higher-end alternative to ATA. A single ATA controller can control two drives. A single SCI controller can control 8 or 16 drives. In addition, SCSI usually offers greater cable length and higher length than ATA.
Wide and Narrow SCSI
Many SCSI standards have options for Wide or Narrow operation. Wide SCSI is parallel SCI which transmits 16 bits of data at a time. Narrow SCSI is parallel SCSI which transmits 8 bits of data at a time.