Scsi3

1 definition found

From The Free On-line Dictionary of Computing (27 SEP 03) [foldoc]:

  SCSI-3
       
           An ongoing standardisation effort to
          extend the capabilities of {SCSI-2}.  SCSI-3's goals are more
          devices on a bus (up to 32); faster data transfer; greater
          distances between devices (longer cables); more device classes


          and command sets; structured documentation; and a structured
          {protocol} model.
       
          In SCSI-2, data transmission is parallel (8, 16 or 32 bit
          wide).  This gets increasingly difficult with higher data
          rates and longer cables because of varying signal delays on
          different wires.  Furthermore, wiring cost and drive power
          increases with wider data words and higher speed.  This has
          triggered the move to serial interfacing in SCSI-3.  By
          embedding clock information into a serial data stream signal
          delay problems are eliminated.  Driving a single signal also
          consumes less driving power and reduces connector cost and
          size.
       
          To allow for backward compatibility and for added flexibility
          SCSI-3 allows the use of several different transport
          mechanisms, some serial and some parallel.  The software
          {protocol} and command set is the same for each transport.
          This leads to a layered protocol definition similar to
          definitions found in networking.
       
          SCSI-3 is therefore in fact the sum of a number of separate
          standards which are defined by separate groups.  These
          standards and groups are currently:
       
           X3T9.2/91-13R2   SCSI-3 Generic Packetized Protocol
           X3T9.2/92-141    SCSI-3 Queuing Model
           X3T9.2/92-079    SCSI-3 Architecture Model
           IEEE P1394       High Performance Serial Bus
           X3T9.2/92-106    SCSI-3 Block Commands
           X3T9.2/91-189    SCSI-3 Serial Bus Protocol
           X3T9.2/92-105    SCSI-3 SCSI-3 Core Commands
          		  SCSI-3 Common Command Set
           X3T9.2/92-108    SCSI-3 Graphic Commands
           X3T9.2/92-109    SCSI-3 Medium Changer Commands
           X3T9.2/91-11     SCSI-3 Interlocked Protocol
           X3T9.2/91-10     SCSI-3 Parallel Interface
           X3T9.2/92-107    SCSI-3 Stream Commands
          		  SCSI-3 Scanner Commands
       
          Additional Documents for the Fibre Channel are also meant to
          be included in the SCSI-3 framework, i.e.:
       
          		  Fibre Channel SCSI Mapping
          		  Fibre Channel Fabric Requirements
          		  Fibre Channel Low Cost Topologies
           X3T9.3/92-007    Fibre Channel Physical and Signalling Interface
          		  Fibre Channel Single Byte Commands
          		  Fibre Channel Cross Point Switch Topology
           X3T9.2/92-103    SCSI-3 Fibre Channel Protocol (GPP & SBP)
       
          As all of this is an ongoing effort of considerable
          complexity, document structure and workgroups may change.  No
          final standard is issued yet.
       
          In the meantime a group of manufacturers have proposed an
          extension of {SCSI-2} called {Ultra-SCSI} which doubles the
          transfer speed of {Fast-SCSI} to give 20MByte/s on an 8 bit
          connection and 40MByte/s on a 16-bit connection.
       
          [Hermann Strass: "SCSI-Bus erfolgreich anwenden",
          Franzis-Verlag Muenchen 1993].
       
          (1995-04-19)