SCSI Standards
1. SCSI-1
ANSI standardized SCSI-1 in 1986. It was then decided by the industry to reach an agreement on a minimal set of 18 basic commands, which came to be known as the Common Command Set (CCS). CCS has the support of all SCSI hardware. This was then considered the basis for SCSI-2.
2. SCSI-2
With the fact of being an advanced version of the initial SCSI that offered additional commands for other types of devices, it also supplied added speed with options referred to as the Fast SCSI and also a 16-bit edition called Wide SCSI. The ability of the SCSI devices to execute commands in the most efficient order was the highlighting feature of SCSI-2. This was called command queuing. Just about all the features and commands available in SCSI-1 are supported by SCSI-2, and a majority of SCSI-1 hardware is called SCSI-2.
3. SCSI-3
Initiated in 1995, SCSI-3 standard is a categorization for a wider set of different SCSI types. SCSI-3 is not deemed to be a standard, but more of a set of different specs, the reason being constant evolution. All of these specs are assembled upon the SCSI Parallel Interface (SPI) that describes a way in which SCSI devices converse with each other. These specs usually start with the word "Ultra", with "Ultra" using SPI1, "Ultra2" using SPI2, and so on.
