SCSI Protocol

SCSI (Small Computer System Interface) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interfaces. It has been a crucial technology in the evolution of computer storage devices.

SCSI is primarily an interface for data transfer between computer components, such as hard drives, optical drives, tape drives, and scanners. Historically, SCSI has been widely used in enterprise environments for high-performance hard disk drives and tape drives, due to its robustness and scalability.

SCSI defines a command set for controlling the devices. This command set is a major feature that distinguishes SCSI from other interface standards and allows for a wide range of devices to be connected with a common interface. Over the years, SCSI has evolved through several standards, including Parallel SCSI (the original standard) and Serial Attached SCSI (SAS), each with enhancements in speed and capabilities.

SCSI standards, particularly in their more recent versions like SAS, support high data transfer rates, making them suitable for high-performance and enterprise applications. SCSI allows multiple devices to be connected in a daisy-chain configuration, enabling one SCSI port to drive several devices.

SAS is a successor to the parallel SCSI interface, providing higher speeds, reduced cable size and cost, and more devices per controller. It's commonly used in enterprise storage systems. SCSI protocols are still relevant in server environments and storage arrays, especially in contexts where multiple hard drives or other storage devices are used.

In consumer products and some business applications, SCSI has largely been replaced by technologies like SATA (Serial ATA), which is simpler and less expensive. However, SCSI remains significant in enterprise and high-performance computing.

Info

While SCSI and ATA (Advanced Technology Attachment) both serve to connect storage devices to computers, SCSI is often considered more robust and feature-rich, supporting a wider range of device types and more devices in a single chain, higher speeds, and more complex command sets. This distinction has historically made SCSI a preference in enterprise and industrial settings.