Computers have been integrated into almost all areas of modern life. They perform a variety of complex tasks and, because of their complexity, computers have many different subsystems. One of these subsystems is the host bus adapter (HBA), a device installed into computers to connect them to networking or storage peripherals.
HBAs come in several forms and can connect to different types of hardware. A host bus adapter can either be integrated into the computer's hardware or installed as a separate circuit board. HBAs come in a few different varieties that are used for connecting to devices using specific connection formats. The most common formats are Fiber Channel, small computer system interface (SCSI), serial advanced technology attachment (SATA), external SATA (eSATA), and universal serial bus (USB).
Fiber Channel is most commonly used to connect computers to networked storage. When the term "host bus adapter" is used generically, it is most often referring to Fiber Channel adapters. Fiber Channel is used most often with large storage devices for networked systems, such as server computers.
SCSI is another format used by a host bus adapter. SCSI is one of the oldest formats still in use by storage devices and HBAs in 2010. SCSI can also be used to connect with other peripherals besides storage devices. Scanners and printers are two examples of the types of peripherals with which SCSI can be used to connect.
The third format used by a host bus adapter, and the most commonly used by typical personal computers (PCs), is SATA. SATA hard drives were the most commonly used type of storage device in 2010. For this reason, SATA HBAs are usually integrated into PC hardware.
ESATA is similar to the standard SATA format. One main difference is that it is designed specifically for connecting to storage devices that are not enclosed in the computer, but are external. Unlike SATA, eSATA is less common and generally requires an HBA to be installed in the form of a circuit board mounted on the computer's chassis.
Another common format of HBA is the USB. The USB format is similar to SCSI in that it can be used both for connections to storage devices and to other peripherals. Like SATA, USB HBAs are often integrated into the hardware of most personal computers.
Host bus adapters are one of the most important subsystems in modern computers. They provide a wide variety of connectivity options, particularly because they can be installed into a system that does not have them already integrated. Without HBAs the vast amounts of data created by computers would have no way to be stored.