SCSI is the “small computer systems interface”, which was originally designed to string many peripherals together onto a single cable/controller.
This included scanners, printers, etc. And would allow daisy chaining different devices.
The advantage of SCSI was that it could be used for drives as well as scanners, CD-ROMS, etc.
Much of the configuration between SCSI devices is completed by the devices themselves, without the need for much input from the user.
SCSI ID and LUNs
Every SCSI device on a single bus is assigned a separate ID number: ID 0 (SCSI controller), ID 2 (HDD), ID 3 (CD-ROM), for example.
Logical Units are defined within each SCSI ID. This is useful if we have an array of drives with a single SCSI connection into the server; the LUN alows us to find an individual drive in the array.
Often the end of the physical SCSI device must be terminated.
SAS Drives
SAS drives are a version of SCSI that uses serial attachments and therefore have no jumpers, terminators, or settings.