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Host adapter
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<h2 id="scsi">SCSI</h2> <p>A SCSI host adapter connects a host system and a peripheral <a href="/facts/SCSI/pxXulrBr">SCSI</a> device or storage system. These adapters manage service and task communication between the host and target.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Typically a <a href="/facts/Device_driver/rDYnHU1G">device driver</a>, linked to the <a href="/facts/Operating_system/8XTuvMh2">operating system</a>, controls the host adapter itself. </p><p>In a typical <a href="/facts/Parallel_SCSI/7dVrf7Lc">parallel SCSI</a> 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). </p><p>The host adapter usually assumes the role of <a href="/facts/SCSI_initiator/dAuwXvS5">SCSI initiator</a>, in that it issues commands to other SCSI devices. </p><p>A computer can contain more than one host adapter, which can greatly increase the number of SCSI devices available. </p><p>Major SCSI adapter manufacturers are <a href="/facts/Hewlett-Packard/abuNSYNu">HP</a>, <a href="/facts/ATTO_Technology/L6jx8pIa">ATTO Technology</a>, Promise Technology, <a href="/facts/Adaptec/Ud19UQ2n">Adaptec</a>, and <a href="/facts/LSI_Corporation/6efkIzMM">LSI Corporation</a>. 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. </p> <h2 id="fibre-channel">Fibre Channel</h2> <p>The term <i>host bus adapter</i> (HBA) may be used to refer to a <a href="/facts/Fibre_Channel/C7C0yreb">Fibre Channel</a> interface card. In this case, it allows devices in a Fibre Channel <a href="/facts/Storage_area_network/e7bmhrmB">storage area network</a> 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.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> Fibre Channel HBAs are available for <a href="/facts/Open_system_(computing)/tVwr9W6r">open systems</a>, computer architectures, and buses, including <a href="/facts/Peripheral_Component_Interconnect/n6CGuFvP">PCI</a> and <a href="/facts/SBus/DMj7dmuL">SBus</a> (obsolete today). </p><p>Each Fibre Channel HBA has a unique <a href="/facts/World_Wide_Name/ffdG9eWj">World Wide Name</a> (WWN), which is similar to an Ethernet <a href="/facts/MAC_address/SVcTfgUH">MAC address</a> in that it uses an <a href="/facts/Organizationally_Unique_Identifier/kSkxCfzX">OUI</a> assigned by the <a href="/facts/IEEE/UddC4pUW">IEEE</a>. 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. </p><p>The major Fibre Channel HBA manufacturers are <a href="/facts/QLogic/vzacJ74I">QLogic</a> and <a href="/facts/Broadcom/pbh0q7ht">Broadcom</a>. As of mid-2009, these vendors shared approximately 90% of the market.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Other manufacturers include <a href="/facts/Agilent_Technologies/wKJ8cvAc">Agilent</a>, <a href="/facts/ATTO_Technology/L6jx8pIa">ATTO</a>, and <a href="/facts/Brocade_Communications_Systems/tMNHxMLm">Brocade</a>. </p><p>HBA is also known to be interpreted as High Bandwidth Adapter in cases of Fibre Channel controllers. </p> <h2 id="infiniband">InfiniBand</h2> <p>The term host channel adapter (HCA) is usually used to describe <a href="/facts/InfiniBand/6CUz47wQ">InfiniBand</a> interface cards.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h2 id="ata">ATA</h2> <p>ATA host adapters are integrated into motherboards of most modern <a href="/facts/Personal_computer/koaYfNce">PCs</a>. They are often improperly called <i>disk controllers</i>. The correct term for the component that allows a computer to talk to a peripheral bus is <i>host adapter</i> . A proper <a href="/facts/Disk_controller/dfRSYlMq">disk controller</a> only allows a <i>disk</i> to talk to the same bus. </p> <h2 id="sas-and-sata">SAS and SATA</h2> <p><a href="/facts/Serial_Attached_SCSI/ekU6NmqQ">SAS</a> 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. </p><p><a href="/facts/Serial_ATA/dW8yAMm8">SATA</a> 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. </p><p>Major SAS/SATA adapter manufacturers are Promise Technologies, <a href="/facts/Adaptec/Ud19UQ2n">Adaptec</a>, <a href="/facts/Hewlett-Packard/abuNSYNu">HP</a>, <a href="/facts/QLogic/vzacJ74I">QLogic</a>, Areca, <a href="/facts/LSI_Logic/6efkIzMM">LSI</a> and <a href="/facts/ATTO_Technology/L6jx8pIa">ATTO Technology</a>. </p> <h3>eSATA</h3> <p><a href="/facts/Serial_ATA/dW8yAMm8">External Serial ATA</a> (eSATA) <a href="/facts/Disk_enclosure/njVoqBh6">disk enclosures</a> and drives are available in the consumer computing market, but not all SATA-compatible motherboards and <a href="/facts/Disk_controller/dfRSYlMq">disk controllers</a> include eSATA ports. As such, adapters to connect eSATA devices to ports on an internal SATA bus are available. </p> <h2 id="mainframe-channel-io">Mainframe channel I/O</h2> <p class="note">Main article: <a href="/facts/Channel_I%2fO/vDBtN2wQ">Channel I/O</a></p> <p>In the <a href="/facts/Mainframe_computer/nrBR6rWa">mainframe</a> field, the terms <i>host adapter</i> or <i>host bus adapter</i> were traditionally not used. A similar goal was achieved since the 1960s with channel I/O, a separate processor that can access <a href="/facts/Main_memory/wPHKFpdx">main memory</a> independently, in parallel with CPU (like later <a href="/facts/Direct_memory_access/DWuVgclV">DMA</a> in <a href="/facts/Personal_computer/koaYfNce">personal computer</a> field), and that executes its own I/O-dedicated <a href="/facts/Computer_program/e38jH9N9">programs</a> when pointed to such by the controlling CPU. </p><p>Protocols used by channel I/O to communicate with <a href="/facts/Peripheral_device/3lEBPE14">peripheral devices</a> include <a href="/facts/ESCON/oYh25l0t">ESCON</a> and newer <a href="/facts/FICON/sX4NCdzH">FICON</a>. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Disk_array_controller/XcbylFek">Disk array controller</a></li> <li><a href="/facts/Fibre_Channel/C7C0yreb">Fibre Channel Host Bus Adapters</a></li> <li><a href="/facts/Host_controller_interface_(USB%2c_Firewire)/NKuGNs02">Host controller interface</a> for USB and FireWire host adapter information</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://hbaapi.sourceforge.net">Fibre Channel Host Bus Adapter API</a></li> <li><a href="http://www.byteparadigm.com/spi-host-adapter-103.html">SPI Host Adapter – Background Information</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Host Adapter". Technopedia. Retrieved 2 July 2019. <a href="https://www.techopedia.com/definition/17146/host-adapter" target="_blank">https://www.techopedia.com/definition/17146/host-adapter</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Rouse, Margaret; Sliwa, Carol (April 2015). "host bus adapter (HBA)". SearchStorage. TechTarget. Retrieved 2 July 2019. <a href="https://searchstorage.techtarget.com/definition/host-bus-adapter" target="_blank">https://searchstorage.techtarget.com/definition/host-bus-adapter</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Host adapter". Computer Hope. <a href="https://www.computerhope.com/jargon/h/host_adapter.htm" target="_blank">https://www.computerhope.com/jargon/h/host_adapter.htm</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Rouse, Margaret; Sliwa, Carol (April 2015). "host bus adapter (HBA)". SearchStorage. TechTarget. Retrieved 2 July 2019. <a href="https://searchstorage.techtarget.com/definition/host-bus-adapter" target="_blank">https://searchstorage.techtarget.com/definition/host-bus-adapter</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Rouse, Margaret; Sliwa, Carol (April 2015). "host bus adapter (HBA)". SearchStorage. TechTarget. Retrieved 2 July 2019. <a href="https://searchstorage.techtarget.com/definition/host-bus-adapter" target="_blank">https://searchstorage.techtarget.com/definition/host-bus-adapter</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Simpson, Dave. "Emulex vs. QLogic: Who's on first?", InfoStor, 2009-08-14. Market share for Q2 2009 according to a proprietary report from Dell'Oro Group. <a href="http://www.infostor.com/index/blogs_new/dave_simpson_storage/blogs/infostor/dave_simpon_storage/post987_8533790865885281755.html" target="_blank">http://www.infostor.com/index/blogs_new/dave_simpson_storage/blogs/infostor/dave_simpon_storage/post987_8533790865885281755.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Mellor, Chris. "HBA market share shenanigans", The Register, 2009-08-14. Also based on Dell'Oro data. <a href="https://www.theregister.co.uk/2009/08/14/hba_market_shares_2009/" target="_blank">https://www.theregister.co.uk/2009/08/14/hba_market_shares_2009/</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Rouse, Margaret; Sliwa, Carol (April 2015). "host bus adapter (HBA)". SearchStorage. TechTarget. Retrieved 2 July 2019. <a href="https://searchstorage.techtarget.com/definition/host-bus-adapter" target="_blank">https://searchstorage.techtarget.com/definition/host-bus-adapter</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> </ol>