computer hardware Computer hardware includes the physical parts of a computer, such as the central processing unit (CPU), random-access memory (RAM), motherboard, computer data storage, graphics card, sound card, and computer case. It includes external devices ...

a host controller, host adapter or host bus adapter (HBA) connects a

computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...

system bus A system bus is a single computer bus that connects the major components of a computer system, combining the functions of a data bus to carry information, an address bus to determine where it should be sent or read from, and a control bus to det ...

which acts as the host system to other

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

and storage devices. The terms are primarily used to refer to devices for connecting

SCSI Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced ...

, SAS,

NVMe NVM Express (NVMe) or Non-Volatile Memory Host Controller Interface Specification (NVMHCIS) is an open, logical-device interface specification for accessing a computer's non-volatile storage media usually attached via the PCI Express bus. The in ...

Fibre Channel Fibre Channel (FC) is a high-speed data transfer protocol providing in-order, lossless delivery of raw block data. Fibre Channel is primarily used to connect computer data storage to Server (computing), servers in storage area networks (SAN) in ...

and

SATA SATA (Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard ...

devices. Devices for connecting to

FireWire IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony a ...

USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...

and other devices may also be called host controllers or host adapters. Host adapters can be integrated in the motherboard or be on a separate

expansion card In computing, an expansion card (also called an expansion board, adapter card, peripheral card or accessory card) is a printed circuit board that can be inserted into an electrical connector, or expansion slot (also referred to as a bus sl ...

. The term

network interface controller A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter and physical network interface) is a computer hardware component that connects a computer to a computer network. Early network interface ...

(NIC) is more often used for devices connecting to computer networks, while the term converged network adapter can be applied when protocols such as

iSCSI Internet Small Computer Systems Interface or iSCSI ( ) is an Internet Protocol-based storage networking standard for linking data storage facilities. iSCSI provides block-level access to storage devices by carrying SCSI commands over a TCP/IP ...

Fibre Channel over Ethernet Fibre Channel over Ethernet (FCoE) is a computer network technology that encapsulates Fibre Channel frames over Ethernet networks. This allows Fibre Channel to use 10 Gigabit Ethernet networks (or higher speeds) while preserving the Fibre Channel ...

allow storage and network functionality over the same physical connection.

SCSI

A connects a host system and a peripheral

device or storage system. These adapters manage service and task communication between the host and target. Typically a

device driver In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabli ...

, linked to the

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

, controls the host adapter itself. In a typical

parallel SCSI Parallel SCSI (formally, SCSI Parallel Interface, or SPI) is the earliest of the interface implementations in the SCSI family. SPI is a parallel bus; there is one set of electrical connections stretching from one end of the SCSI bus to the ot ...

subsystem, each device has assigned to it a unique numerical ID. As a rule, the host adapter appears as SCSI ID 7, which gives it the highest priority on the SCSI bus (priority descends as the SCSI ID descends; on a 16-bit or "wide" bus, ID 8 has the lowest priority, a feature that maintains compatibility with the priority scheme of the 8-bit or "narrow" bus). The host adapter usually assumes the role of

SCSI initiator In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSI command. The initiator usually does not provide any Logical Unit Numbers (LUNs). On the other hand, a SCSI target is the endpoint tha ...

, in that it issues commands to other SCSI devices. A computer can contain more than one host adapter, which can greatly increase the number of SCSI devices available. Major SCSI adapter manufacturers are HP,

ATTO Technology ATTO Technology, Inc. is a manufacturer of storage connectivity products for data-intensive computing. ATTO manufactures Fibre Channel and SAS (software), SAS/SATA host bus adapters, Fibre Channel host bus adapters, protocol converter, protocol ...

, Promise Technology,

Adaptec Adaptec, Inc., was a computer storage company and remains a brand for computer storage products. The company was an independent firm from 1981 to 2010, at which point it was acquired by PMC-Sierra, which itself was later acquired by Microsemi, ...

, and

LSI Corporation LSI Logic Corporation was an American company founded in Santa Clara, California, was a pioneer in the ASIC and EDA industries. It evolved over time to design and sell semiconductors and software that accelerated storage and networking in dat ...

. LSI, Adaptec, and ATTO offer PCIe SCSI adapters which fit in Apple Mac, on Intel PCs, and low-profile motherboards which lack SCSI support due to the inclusion of SAS and/or SATA connectivity.

Fibre Channel

The term ''host bus adapter'' (HBA) may be used to refer to a

interface card. In this case, it allows devices in a Fibre Channel

storage area network A storage area network (SAN) or storage network is a computer network which provides access to consolidated, block device, block-level data storage. SANs are primarily used to access Computer data storage, data storage devices, such as disk ...

to communicate data between each otherit may connect a server to a switch or storage device, connect multiple storage systems, or connect multiple servers. Fibre Channel HBAs are available for open systems, computer architectures, and buses, including

PCI PCI may refer to: Business and economics * Payment card industry, businesses associated with debit, credit, and other payment cards ** Payment Card Industry Data Security Standard, a set of security requirements for credit card processors * Prov ...

and SBus (obsolete today). Each Fibre Channel HBA has a unique

World Wide Name A World Wide Name (WWN) or World Wide Identifier (WWID) is a unique identifier used in storage technologies including Fibre Channel, Parallel ATA, Serial ATA, SCSI and Serial Attached SCSI (SAS). A WWN may be employed in a variety of roles, s ...

(WWN), which is similar to an Ethernet

MAC address A MAC address (short for medium access control address or media access control address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use i ...

in that it uses an OUI assigned by the

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is an American 501(c)(3) organization, 501(c)(3) public charity professional organization for electrical engineering, electronics engineering, and other related disciplines. The IEEE ...

. However, WWNs are longer (8 bytes). There are two types of WWNs on a HBA; a node WWN (WWNN), which is shared by all ports on a host bus adapter, and a port WWN (WWPN), which is unique to each port. There are HBA models of different speeds: 1 Gbit/s, 2 Gbit/s, 4 Gbit/s, 8 Gbit/s, 10 Gbit/s, 16 Gbit/s, 20 Gbit/s and 32 Gbit/s. The major Fibre Channel HBA manufacturers are QLogic and

Broadcom Broadcom Inc. is an American multinational corporation, multinational designer, developer, manufacturer, and global supplier of a wide range of semiconductor and infrastructure software products. Broadcom's product offerings serve the data cen ...

. As of mid-2009, these vendors shared approximately 90% of the market.Mellor, Chris
"HBA market share shenanigans"
''The Register'', 2009-08-14. Also based on Dell'Oro data. Other manufacturers include Agilent, ATTO, and

Brocade Brocade () is a class of richly decorative shuttle (weaving), shuttle-woven fabrics, often made in coloured silks and sometimes with gold and silver threads. The name, related to the same root as the word "broccoli", comes from Italian langua ...

. HBA is also known to be interpreted as High Bandwidth Adapter in cases of Fibre Channel controllers.

InfiniBand

The term (HCA) is usually used to describe

InfiniBand InfiniBand (IB) is a computer networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used ...

interface cards.

ATA

ATA host adapters are integrated into motherboards of most modern PCs. They are often improperly called ''disk controllers''. The correct term for the component that allows a computer to talk to a peripheral bus is ''host adapter'' . A proper

disk controller A disk controller is a controller circuit that enables a CPU to communicate with a hard disk, floppy disk or other kind of disk drive. It also provides an interface between the disk drive and the bus connecting it to the rest of the system.{ ...

only allows a ''disk'' to talk to the same bus.

SAS and SATA

SAS or serial-attached SCSI is the current connectivity to replace the previous generation parallel-attached SCSI (PAS) devices. Ultra320 was the highest level of parallel SCSI available, but SAS has since replaced it as the highest-performing SCSI technology.

is a similar technology from the aspect of connection options. HBAs can be created using a single connector to connect both SAS and SATA devices. Major SAS/SATA adapter manufacturers are Promise Technologies,

, HP, QLogic, Areca, LSI and

eSATA

External Serial ATA (eSATA)

disk enclosure A disk enclosure is a specialized casing designed to hold and power hard disk drives or solid state drives while providing a mechanism to allow them to communicate to one or more separate computers. Drive enclosures provide power to the drives ...

s and drives are available in the consumer computing market, but not all SATA-compatible motherboards and

s include eSATA ports. As such, adapters to connect eSATA devices to ports on an internal SATA bus are available.

Mainframe channel I/O

In the

mainframe A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...

field, the terms ''host adapter'' or ''host bus adapter'' were traditionally not used. A similar goal was achieved since the 1960s with channel I/O, a separate processor that can access

main memory Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processin ...

independently, in parallel with CPU (like later DMA in

personal computer A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...

field), and that executes its own I/O-dedicated programs when pointed to such by the controlling CPU. Protocols used by channel I/O to communicate with

peripheral device A peripheral device, or simply peripheral, is an auxiliary hardware device that a computer uses to transfer information externally. A peripheral is a hardware component that is accessible to and controlled by a computer but is not a core compo ...

s include

ESCON ESCON (Enterprise Systems Connection) is a data connection created by IBM, and is commonly used to connect their mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large o ...

and newer

FICON FICON (Fibre Connection) is the IBM proprietary name for the ANSI ''FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol'' for Fibre Channel (FC) protocol. It is a FC layer 4 protocol used to map both IBM's antecedent (either ESCON or para ...

References

{{Reflist

External links

Fibre Channel Host Bus Adapter API
Computer buses SCSI