Host adapter
 |
This article may require cleanup to meet Wikipedia's quality standards. (Consider using more specific cleanup instructions.) Please help improve this article if you can. The talk page may contain suggestions. (January 2012) |
In computer hardware, a host controller, host adapter, or host bus adapter (HBA) connects a host system (the computer) to other network and storage devices. The terms are primarily used to refer to devices for connecting SCSI, Fibre Channel and eSATA devices, but devices for connecting to IDE, Ethernet, FireWire, USB and other systems may also be called host adapters. Recently, the advent of iSCSI and Fibre Channel over Ethernet has brought about Ethernet HBAs, which are different from Ethernet NICs in that they include TCP Offload Engines. There are also converged HBAs that support both Ethernet and Fibre Channel called Converged Network Adapters (CNAs).
Contents |
[edit] SCSI
A SCSI host adapter connects host system to boot from a SCSI device, but also facilitates configuration of the host adapter. 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 HP, ATTO Technology, Promise Technology, Adaptec, and LSI Logic. LSI, Adaptec, and ATTO currently offer PCIe SCSI adapters which fit in new Apple Mac, on Intel PCs, and low-profile motherboards from companies like HP (which now lack SCSI support due to the inclusion of SAS and/or SATA connectivity)....
[edit] Fibre Channel
Today, the term host bus adapter (HBA) is most often used to refer to a Fibre Channel interface card. Fibre Channel HBAs are available for all major open systems, computer architectures, and buses, including PCI and SBus (obsolete today). Each HBA has a unique World Wide Name (WWN), which is similar to an Ethernet MAC address in that it uses an 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: 1Gbit/s, 2Gbit/s, 4Gbit/s, 8Gbit/s, 10Gbit/s and 20Gbit/s.
The major Fibre Channel HBA manufacturers are QLogic and Emulex. As of mid-2009, these vendors shared approximately 90% of the market.[1][2] Other manufacturers include Agilent, ATTO, Brocade, and LSI.
HBA is also known to be interpreted as High Bandwidth Adapter in cases of Fibre Channel controllers.
[edit] InfiniBand
The term host channel adapter (HCA) is usually used to describe InfiniBand interface cards.
[edit] 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[citation needed]. A proper disk controller only allows a disk to talk to the same bus.
[edit] 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.
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 and ATTO Technology.
[edit] eSATA
External Serial ATA disk enclosures and drives are increasingly common[citation needed] in the consumer computing market, but not all SATA-compatible motherboards and disk controllers include external SATA ports. As such, adapters to connect external SATA devices to ports on an internal SATA bus are commonly available.
[edit] Mainframe I/O channels
In the mainframe field, the terms host adapter or host bus adapter were traditionally not used. A similar goal is achieved since 1960s with a different technique: I/O channel, or simply channel, is a separate processor that can access main memory independently, in parallel with CPU (like later DMA in personal computer field), and that executes its own I/O-dedicated programs when pointed to such by the controlling CPU.
Protocols used by I/O channels to communicate with peripheral devices include ESCON and newer FICON.
[edit] Where to Acquire HBA's and Controllers
 |
This article contains instructions, advice, or how-to content. The purpose of Wikipedia is to present facts, not to train. Please help improve this article either by rewriting the how-to content or by moving it to Wikiversity or Wikibooks. (February 2012) |
|
|
This article uses first-person ("I"; "we") or second-person ("you") inappropriately. Please rewrite it to use a more formal, encyclopedic tone. (February 2012) |
|
|
This article may require cleanup to meet Wikipedia's quality standards. (Consider using more specific cleanup instructions.) Please help improve this article if you can. The talk page may contain suggestions. (January 2012) |
Controllers are best if bought from Manufacturers; using generic spare parts is frowned upon not strictly because of the lack of authenticity, but because of the compatibility and quality of the generic part. In many instances, the most important drawback is - the loss of the manufacturer's warranty when using generic or fake "china" products. Most SCSI and SAS drives are available through their respective Manufacturer's sites. Additionally however, one may look to resellers for parts, as often they sell controllers, hba's, peripherals, and components at deeper discounts than the manufacturer due to sales targets, high overheads, and company policies of inventory turnaround. A reliable source for computer hardware is difficult to come across, but you can be smart and search eBay, and sort the sellers by their feedback ratings - platinum power sellers are generally reliable companies, although this is not the golden rule of online IT Purchase. If possible - you should look to visit the reseller - see their stock, make sure its all official goods. Try not to buy from companies that only sell used items, as you're more likely to be stuck with a defective product which may be out of warranty. Check your reseller's history on BBB - the better business bureau - look out for complaints and dishonest practice. Also - ask if the company you're dealing with has a DBA or has previously done business as another company. Lastly, look to see how long the company you want to buy from has been dealing in the field of IT. Generally speaking, the longer they're in the industry - the longer they've been selling product - and the more likely you are to have found a good source for product. A personal favorite reseller for server components and peripherals is New York Computer Exchange. Good luck in your hunt for the right adapter. [3]
[edit] See also
- Network card
- Fibre Channel Host Bus Adapters
- Converged Network Adapter (CNA)
- Host controller interface for USB and FireWire host adapter information
[edit] References
- ^ 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.
- ^ Mellor, Chris. "HBA market share shenanigans", The Register, 2009-08-14. Also based on Dell'Oro data.
- ^ "Single channel Ultra320 SCSI host bus adapter G2". http://h18004.www1.hp.com/products/servers/proliantstorage/adapters/singlechannel/index.html. Retrieved 12/20/2011.
