This is not Wide SCSI. It is also not Ultra SCSI. In fact, the SCSI 3 specification does not exist yet. When it is created, it will probably use some sort of Fiber-channel interface. However, Wide SCSI or Ultra-SCSI are sometimes referred to as SCSI-3.
The SCSI-3 specification is designed to further improve functionality and accommodate high-speed serial transmission interfaces. To do so, SCSI was effectively "layered" logically. This layering allowed the software interfaces to remain relatively unchanged while accommodating new physical interconnect schemes based upon serial interconnects such as Fibre Channel and Serial Storage Architecture (SSA).
The current SCSI specification, which adds features to the SCSI-2 standard.
The current SCSI specification that defines the command formats used in the SCSI protocol.
change the document structure, SCSI-3 is not one document with all the different layers and electrical interfaces, but a collection of documents that cover the physical layer, the basic protocol specific to that electrical interface, the primary command set layer (SPC) and the specific protocol layer. The specific protocol layer contains the Hard Disk interface Commands in the Block Commands (SBC), Stream Commands for tape drives(SSC), Controller Commands for RAID arrays (SCC), Multimedia Commands (MMC), Media Changer Commands (MCC) and enclosure services commands (SES) for example. There is an overall architectural model (SAM). Each document has its own revision level, these are normally referred to as SCSI, the –3 has been dropped.
The third generation of SCSI; introduces Fast-20 and Fast-40 as improvements to the parallel bus. The standard also includes a number of specifications for high-speed serial bus architectures such as SSA, Fibre Channel, and IEEE 1394.
The SCSI 3 specification doesn't technically exist, but SCSI-3 is often used to describe the Ultra SCSI standard. Before the time of Ultra SCSI, SCSI-3 was a misnomer for Fast Wide SCSI-2.
This term describes a set of related standards that are currently being developed. The SCSI-3 standards are layered to allow substitution of parts of the structure as new technology emerges. For example, a comparable set of standards for a SCSI Fiber Channel interface disc drive replaces the physical and protocol layers with new documents but uses the same documents for the other 3 "layers". The basic layers are: physical (connectors, pin assignments, electrical specifications), protocol (description of how physical layer activity is organized into bus phases, packets, etc.), architecture (a description of how command requests are organized, queued, responded to by any protocol), primary commands (description of commands that must be supported by all SCSI devices), and device specific commands (commands that are specific to a particular class of devices; CD-ROMs or WORM drives, for example).
