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Incomputer hardware ahost controller,host adapter orhost bus adapter (HBA) connects acomputersystem bus which acts as the host system to othernetwork andstorage devices.[1] The terms are primarily used to refer to devices for connectingSCSI,SAS,NVMe,Fibre Channel andSATA devices.[2] Devices for connecting toFireWire,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 separateexpansion card.[3]
The termnetwork interface controller (NIC) is more often used for devices connecting to computer networks, while the termconverged network adapter can be applied when protocols such asiSCSI orFibre Channel over Ethernet allow storage and network functionality over the same physical connection.
ASCSI host adapter connects a host system and a peripheralSCSI device or storage system. These adapters manage service and task communication between the host and target.[2] Typically adevice driver, linked to theoperating system, controls the host adapter itself.
In a typicalparallel 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 ofSCSI 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 areHP,ATTO Technology, Promise Technology,Adaptec, andLSI 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.
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The termhost bus adapter (HBA) may be used to refer to aFibre Channel interface card. In this case, it allows devices in a Fibre Channelstorage area network to communicate data between each other – it may connect a server to a switch or storage device, connect multiple storage systems, or connect multiple servers.[2] Fibre Channel HBAs are available foropen systems, computer architectures, and buses, includingPCI andSBus (obsolete today).
Each Fibre Channel HBA has a uniqueWorld Wide Name (WWN), which is similar to an EthernetMAC address in that it uses anOUI assigned by theIEEE. 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 areQLogic andBroadcom. As of mid-2009, these vendors shared approximately 90% of the market.[4][5] Other manufacturers includeAgilent,ATTO, andBrocade.
HBA is also known to be interpreted as High Bandwidth Adapter in cases of Fibre Channel controllers.
The termhost channel adapter (HCA) is usually used to describeInfiniBand interface cards.[2]
ATA host adapters are integrated into motherboards of most modernPCs. They are often improperly calleddisk controllers. The correct term for the component that allows a computer to talk to a peripheral bus ishost adapter[citation needed]. A properdisk controller only allows adisk to talk to the same bus.
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.
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,HP,QLogic, Areca,LSI andATTO Technology.
External Serial ATA (eSATA)disk enclosures and drives are available in the consumer computing market, but not all SATA-compatible motherboards anddisk controllers include eSATA ports. As such, adapters to connect eSATA devices to ports on an internal SATA bus are available.
In themainframe field, the termshost adapter orhost bus adapter were traditionally not used.A similar goal was achieved since the 1960s with channel I/O, a separate processor that can accessmain memory independently, in parallel with CPU (like laterDMA inpersonal computer field), and that executes its own I/O-dedicatedprograms when pointed to such by the controlling CPU.[citation needed]
Protocols used by channel I/O to communicate withperipheral devices includeESCON and newerFICON.