What is Small Computer System Interface (SCSI)?
Last Updated :
18 Oct, 2023
Data transfer and data storage are very important aspects in the world of computing. That evolved significantly over the years. One of the leading technologies in this field is the Small Computer System Interface(or SCSI). It provides a high level of versatility and efficiency in data transfer. and also Played an important role in connecting and managing various peripheral devices. In this article, we will learn in detail about the world of SCSI.
What is a Small Computer System Interface(SCSI)?
SCSI (pronounced SKUH-zee and sometimes known colloquially as "skuzy"), short for Computer System Interface, is a set of American National Standards Institute (ANSI) standard electronic interfaces used for computers. Allows communication with peripheral hardware such as disk drives, tape drives, CD-ROM drives, printers, and scanners faster and more flexible than previous parallel data transfer interfaces.
Small Computer System Interface(SCSI)
SCSI Host Adapter
A SCSI host adapter is a device used to connect one or more SCSI devices to a computer bus. A SCSI host adapter is commonly referred to as a SCSI controller, which is not entirely accurate, as any component that understands the SCSI protocol can be called a controller. In this notion, all SCSI devices have a SCSI controller integrated, while host adapters are responsible for transferring data between the computer's input/output bus and the SCSI bus.
SCSI Devices
SCSI Devices encompass a wide range of peripherals, including hard drives, CD/DVD drives, tape recording drives, scanners, and printers. These devices are designed to connect to a SCSI machine and communicate with the host computer through the SCSI host appendage. A SCSI machine is the physical connection through which SCSI bias are connected to the SCSI host appendage. It can be either internal or external, depending on the configuration of the computer and the bias.
Small Computer System Interface(SCSI) and Tools
Although not all devices support all levels of SCSI, SCSI standards are generally backward-compatible. That is, if an older peripheral device is connected to a newer computer with support for a later standard, the older device will operate at an older and slower data rate. In personal computing, the SCSI interface has for the most part been replaced by Universal Serial Bus (USB). In the enterprise, SCSI is still used in server farms for hard drive controllers.
SCSI Components
There are several components are used in SCSI storage systems.
- Initiator: An initiator issues requests for service by SCSI devices and receives responses. Initiators come in various forms and may be integrated into the server's system board or exist within the host bus adapter. iSCSI connectivity typically uses a software-based initiator.
- Target: The SCSI target is typically a physical storage device (although software-based SCSI targets also exist). The target can be a single hard disk or an entire storage array. It is also possible for non-storage hardware to act as a SCSI target. Although rare today, it was once common to connect an optical scanner to a computer via a SCSI bus and act as a SCSI target.
- Service Delivery Subsystem: The mechanism that allows communication between the initiator and the target; This usually takes the form of cabling.
- Expander: Used only with serial-attached SCSI (SAS) Allows multiple SAS devices to share a single initiator port.
Serial - Attached SCSI
- SAS products are compatible with devices that use earlier SCSI technologies. The Serial Storage Architecture (SSA) standard can be used when SCSI performance is not sufficient, such as iSCSI, which embeds SCSI-3 over TCP/IP (most SCSI-3 specification designations begin with Ultra). Preserves command sets.
- SAS has become a popular alternative to parallel SCSI in enterprise environments. Both serial and parallel SCSI are based on the SCSI command set. SAS Parallel offers the following distinct advantages over SCSI:
- It supports up to 65,535 devices (through the use of an extender). The latest parallel SCSI standards allow only 16 devices.
- This eliminates the problems of termination and clock malfunction.
- It is a point-to-point technology. This means that SAS is not subject to the resource contention issues that are so common with parallel SCSI.
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