View source for Host adapter

{{Short description|Computer hardware device}}
{{refimprove|date=February 2017}}

[[File:QLA 2200F.jpg|thumb |upright=1.3 |Fibre Channel host bus adapter (a [[64-bit]] [[PCI-X]] card){{clarify|What in the picture does the caption describe?|date=August 2023}}]]
[[File:Controller SCSI.JPG|thumb |upright=1.3 |SCSI host adapter (a [[16-bit]] [[Industry Standard Architecture|ISA]] card)]]

In [[computer hardware]] a '''host controller''', '''host adapter''' or '''host bus adapter''' ('''HBA''') connects a [[computer]] [[system bus]] which acts as the host system to other [[computer network|network]] and [[computer storage|storage]] devices.<ref>{{cite web |url=https://www.techopedia.com/definition/17146/host-adapter |title=Host Adapter |website=Technopedia |date=4 January 2017 |access-date=2 July 2019}}</ref> The terms are primarily used to refer to devices for connecting [[SCSI]], [[Serial Attached SCSI|SAS]], [[NVMe]], [[Fibre Channel]] and [[Serial ATA|SATA]] devices.<ref name="techtarget">{{cite web |url=https://searchstorage.techtarget.com/definition/host-bus-adapter |title=host bus adapter (HBA) |website=SearchStorage |publisher=TechTarget |last1=Rouse |first1=Margaret |last2=Sliwa |first2=Carol |access-date=2 July 2019 |date=April 2015}}</ref> Devices for connecting to [[FireWire]], [[USB]] 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]].<ref name="computerhope">{{cite web |url=https://www.computerhope.com/jargon/h/host_adapter.htm |title=Host adapter |work=Computer Hope}}</ref>

The term [[network interface controller]] (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]] or [[Fibre Channel over Ethernet]] allow storage and network functionality over the same physical connection.

==SCSI==
A '''{{vanchor|SCSI host adapter}}''' connects a host system and a peripheral [[SCSI]] device or storage system. These adapters manage service and task communication between the host and target.<ref name="techtarget" /> Typically a [[device driver]], linked to the [[operating system]], controls the host adapter itself.

In a typical [[parallel SCSI]] 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 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 [[Hewlett-Packard|HP]], [[ATTO Technology]], Promise Technology, [[Adaptec]], and [[LSI Corporation]]. 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==
[[File:Host-Bus-Adapter-(HBA).jpg|thumb|Fibre Channel host bus adapter]]
The term ''host bus adapter'' (HBA) may be used to refer to a [[Fibre Channel]] interface card. In this case, it allows devices in a Fibre Channel [[storage area network]] to communicate data between each other{{snd}}it may connect a server to a switch or storage device, connect multiple storage systems, or connect multiple servers.<ref name="techtarget" /> Fibre Channel HBAs are available for [[Open system (computing)|open systems]], computer architectures, and buses, including [[Peripheral Component Interconnect|PCI]] and [[SBus]] (obsolete today).

Each Fibre Channel HBA has a unique [[World Wide Name]] (WWN), which is similar to an Ethernet [[MAC address]] in that it uses an [[Organizationally Unique Identifier|OUI]] assigned by 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&nbsp;Gbit/s, 2&nbsp;Gbit/s, 4&nbsp;Gbit/s, 8&nbsp;Gbit/s, 10&nbsp;Gbit/s, 16&nbsp;Gbit/s, 20&nbsp;Gbit/s and 32&nbsp;Gbit/s.

The major Fibre Channel HBA manufacturers are [[QLogic]] and [[Broadcom]]. As of mid-2009, these vendors shared approximately 90% of the market.<ref>Simpson, Dave. [http://www.infostor.com/index/blogs_new/dave_simpson_storage/blogs/infostor/dave_simpon_storage/post987_8533790865885281755.html "Emulex vs. QLogic: Who's on first?"], ''InfoStor'', 2009-08-14. Market share for Q2 2009 according to a proprietary report from [http://www.delloro.com/ Dell'Oro Group].</ref><ref>Mellor, Chris. [https://www.theregister.co.uk/2009/08/14/hba_market_shares_2009/ "HBA market share shenanigans"], ''The Register'', 2009-08-14. Also based on Dell'Oro data.</ref> Other manufacturers include [[Agilent Technologies|Agilent]], [[ATTO Technology|ATTO]], and [[Brocade Communications Systems|Brocade]].

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

==InfiniBand==
The term '''{{visible anchor|host channel adapter}}''' ('''HCA''') is usually used to describe [[InfiniBand]] interface cards.<ref name="techtarget" />

==ATA==
ATA host adapters are integrated into motherboards of most modern [[Personal computer|PC]]s. 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'' {{Citation needed|date=November 2007}}. A proper [[disk controller]] only allows a ''disk'' to talk to the same bus.

==SAS and SATA==
[[File:LSI_9207-4i4e_PCI-E_SAS_HBA.jpg|thumb|SAS host adapter]]
[[Serial Attached SCSI|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.

[[Serial ATA|SATA]] 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, [[Adaptec]], [[Hewlett-Packard|HP]], [[QLogic]], Areca, [[LSI Logic|LSI]] and [[ATTO Technology]].

===eSATA===
[[Serial ATA#eSATA|External Serial ATA]] (eSATA) [[disk enclosure]]s and drives are available in the consumer computing market, but not all SATA-compatible motherboards and [[disk controller]]s include eSATA ports. As such, adapters to connect eSATA devices to ports on an internal SATA bus are available.

==Mainframe channel I/O==
{{Main|Channel I/O}}
In the [[mainframe computer|mainframe]] 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]] independently, in parallel with CPU (like later [[Direct memory access|DMA]] in [[personal computer]] field), and that executes its own I/O-dedicated [[computer program|program]]s when pointed to such by the controlling CPU.{{cn|reason=Broad statement which is hard to verify –  is there a specific example of this?|date=July 2019}}

Protocols used by channel I/O to communicate with [[peripheral device]]s include [[ESCON]] and newer [[FICON]].

==See also==
* [[Disk array controller]]
* [[Fibre Channel#Host_bus_adapters|Fibre Channel Host Bus Adapters]]
* [[Host controller interface (USB, Firewire)|Host controller interface]] for USB and FireWire host adapter information

==References==
{{Reflist}}

==External links==
*[http://hbaapi.sourceforge.net Fibre Channel Host Bus Adapter API]
*[http://www.byteparadigm.com/spi-host-adapter-103.html SPI Host Adapter – Background Information]

[[Category:Computer buses]]
[[Category:SCSI]]