What (who) is SCSI adaptors - definition

SCSI target; SCSI initiator

Fast SCSI

ORIGINAL SCSI COMPUTER STORAGE BUS

SCSI1; SCSI-1; SCSI-2; SCSI2; SCSI-3; SCSI3; Fast SCSI; Wide SCSI; Ultra SCSI; Narrow SCSI; LVD SCSI; Ultra-160; Ultra SCSI-2; Ultra SCSI-3; Ultra-320; Ultra-640; Fast-320; Differential SCSI; Ultra-3; Ultra-2; SCSI Parallel Interface; Ultra2 SCSI; SCSI terminating resistor; Scsi terminating resistor; Quick arbitration and selection

<hardware> A variant on the SCSI-2 bus. It uses the same 8-bit bus as the original SCSI-1 but runs at up to 10MB/s - double the speed of SCSI-1. (1994-11-24)

SCSI-2

ORIGINAL SCSI COMPUTER STORAGE BUS

<hardware> A version of the SCSI command specification. SCSI-2 shares the original SCSI's asynchronous and synchronous modes and adds a "Fast SCSI" mode ( < 10MB/s ) and "Wide SCSI" (16 bit, < 20MB/s or rarely 32 bit). Another major enhancement was the definition of command sets for different device classes. SCSI-1 was rather minimalistic in this respect which led to various incompatibilities especially for devices other than hard-disks. SCSI-2 addresses that problem. allowing scanners, {hard disk drives}, CD-ROM drives, tapes and many other devices to be connected. Normal SCSI-2 equipment (not wide or differential) can be connected to a SCSI-1 bus and vice versa. (1995-04-19)

Wide SCSI

ORIGINAL SCSI COMPUTER STORAGE BUS

<hardware, standard> A variant on the SCSI-2 interface. It uses a 16-bit bus - double the width of the original SCSI-1 - and therefore cannot be connected to a SCSI-1 bus. It supports transfer rates up to 20 MB/s, like Fast SCSI. There is also a SCSI-2 definition of Wide-SCSI with a 32 bit data bus. This allows up to 40 megabytes per second but is very rarely used because it requires a large number of wires (118 wires on two connectors). Thus Wide SCSI usually means 16 bit-wide SCSI. (1995-04-21)

Wikipedia

SCSI initiator and target

In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSI command. The initiator usually does not provide any Logical Unit Numbers (LUNs).

On the other hand, a SCSI target is the endpoint that does not initiate sessions, but instead waits for initiators' commands and provides required input/output data transfers. The target usually provides to the initiators one or more LUNs, because otherwise no read or write command would be possible.

https://en.wikipedia.org/wiki/SCSI initiator and target