Information Storage and Management: Storing, Managing, and Protecting Digital Information in Classic, Virtualized, and Cloud Environments, Second Edition

Appendix B

Parallel SCSI

Shugart Associates and NCR developed a system interface in 1981 and named it Shugart Associates System Interface (SASI). SASI was developed to build a proprietary, high-performance standard, primarily for use by these two companies. However, to increase the acceptance of SASI in the industry, the standard was updated to a more robust interface and renamed SCSI. In 1986, the American National Standards Institution (ANSI) acknowledged the new SCSI as an industry standard.

SCSI, first developed for hard disks, is often compared to IDE/ATA. SCSI offers improved performance, scalability, and compatibility options, making it suitable for high-end computers. However, the high cost associated with SCSI limits its popularity among home or business desktop users.

Prior to the development of SCSI, the interfaces used for communication between devices varied with each device. For example, an HDD interface could be used only with a hard disk drive. SCSI was developed to provide a device-independent mechanism for attaching to and accessing host computers. SCSI also provided an efficient peer-to-peer I/O bus that supported multiple devices. Today, SCSI is commonly used as a hard disk interface. However, SCSI can be used for connecting devices, such as tape drives, printers, and optical media drives, to the host computer without modifying the system hardware or software. Over the years, SCSI has undergone radical changes and has evolved into a robust industry standard. ...