Detailed explanation of SCSI Storage and implementation of ISCSI in Linux

I. Overview

SCSI was originally an I/O technology designed specifically for small computer systems. However, due to its architecture and Protocol advantages, SCSI was widely used in the implementation of the underlying technologies of DAS and SAN.

SCSI definition:

SCSI: Small Computer System Interface

SCSI is an I/O technology.

SCSI standardizes a parallel I/O bus and related Protocols

SCSI data transmission is performed in blocks.

Features of SCSI:

Device independence

Multi-device parallel

High bandwidth

Low system overhead

SCSI bus:

The SCSI bus is the path for data transmission between SCSI devices.

The SCSI bus is also called a SCSI channel.

SCSI Terminator:

The SCSI Terminator is located at the end of the SCSI bus to reduce mutual signal and maintain constant voltage on the SCSI chain.

The last SCSI device of the SCSI chain needs to use the Terminator.

The Terminator is not required for the intermediate device on the SCSI chain.

SCSI controller:

The SCSI bus communicates with devices such as hard disks through the SCSI controller.

The SCSI controller can be logically divided into one task management unit and multiple logical units (LU)

Scsi id:

An independent SCSI bus can support 8 or 16 SCSI devices according to different specifications. The serial numbers of devices must be controlled by the scsi id, each SCSI device in the system must have its own unique scsi id, which is actually the address of these devices, A narrow SCSI bus can be up to 8 and a wide SCSI bus can be connected to a maximum of 16 different SCSI devices.

LUN:

LUN (Logical Unit Number) is a method introduced to use and describe more devices and objects. Each scsi id can contain up to 32 Luns, a lun corresponds to a logical device.

SCSI connection:

SCSI communication mode:

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