SAS or Serial Attached SCSI, and SCSI or Small Computer System Interface are interfaces used within computers to get data stored in computers. Initially, SCSI was created to handle small data amounts.
However, it has been improved to support the transfer of large data amounts. With SCSI, you can connect more devices at the same time. Hard drives, CD-ROM drives, Printers are examples of devices that can connect to SCSI. On the other hand, SAS is a more recent technology than SCSI. You can also see it as an improved version of SCSI.
SAS was introduced to improve on some of the limitations of SCSI. For instance, SAS is a serial device rather than a parallel device like SCSI. As a result, you can connect more devices to your computer than you can do with SCSI. However, one of the advantages of SCSI over SAS is that it has a higher transfer speed.