Overview of HBA

A Host Bus Adapter (HBA) is a printed circuit board and/or IC adapter that provides input/output (I/O) processing and physical connectivity between servers and storage devices. Because HBAs offload the host CPU during data retrieval and storage tasks, they can improve server performance. An HBA and a disk subsystem connected to it is sometimes called a disk channel.
General definition of HBA – I/O adapter that connects the host I/O bus and the computer’s memory system. According to this definition, because the video card is connected to the computer and memory, the network card is connected to the network bus and memory, and the SCSI-FC card is connected to the SCSI or FC bus and memory, they are considered to be is the HBA. HBA includes FC-HBA and iSCSI HBA and other HBAs in the future, but HBA is commonly used in SCSI. Adapters and network cards are used for FC, in addition network cards are used for Ethernet and Token Ring networks.
We know that a computer is connected mainly by two buses (of course, the actual situation will be different, here we only discuss the common and simple situation), one called the system bus, one The I/C bus is called the S bus. The system bus on the CPU, memory, cache, etc., the I/O bus is a peripheral device and currently the most common is the PCI bus. The two buses are connected by a chip or bridge circuit. For example, the city has 2 main roads, one in the administrative area, the other in the commercial area, in the middle there is a roundabout, two main roads are connected, how is the bus system. the main street in the district and the I/O bus is the same as the main street in the business district. It should be remembered that the bandwidth unit of the system bus and the I / O bus is GB, but it is clear that the main road and the business district of the district compared to the trunk road, the former road is definitely more “central”, wider, smoother, high design requirements.
Although the I/O bus speed is much lower than the system bus bandwidth, the result is Gbyte to measure anyway and we know the speed of the devices is usually only a few hundred trillion or even tens of k, How does coordination work? It’s easy, we’ll arrange the peripherals, connect to the I/O bus or more! HBA refers to Host and I/O BUS directly to an adapter, but just as a plumber would often say “pass twice”. The role of the HBA is to realize the PCI or Sbus internal channel protocol and convert the Fiber Channel protocol between.

The importance of HBA

In the first SAN storage system, the data transmission of the server and the switch is through fiber optic cable, because the server is a SCSI instruction for the storage device, the ordinary LAN IP protocol cannot be used, therefore need to use FC transmission, so this SAN is called FC-SAN, later appeared in the IP SAN protocol package, can take ordinary LAN, called IP-SAN, the most typical today is Popular ISCSI.
Both of these methods require decompression of heavy data packets. Therefore, a high-performance SAN system requires a dedicated network adapter to decompress the server to reduce the load on the processor. This network card is called HBA card, of course, in addition to decompression work, can also provide a fiber interface (if the iSCSI HBA card provides a common RJ45 interface) for the corresponding conversion connection; HBA physically, you can plug it into a PCI or PCI slot like a network card, so the usage of this device is very similar to a network card and many people confuse it with a regular network card or a fiber optic card. often. Of course, some iSCSI HBA cards can be used as a normal network card, but it would be very uneconomical considering the price.

HBA Principle

Common data transfer protocols between the server and the storage device are IDE, SCSI and Fiber Channel. To establish communication between the server and the storage device, the same communication protocol is required at both ends of the communication. Controllers are typically available on the storage device, and the controller implements one or more communication protocols that allow conversion between storage protocols such as IDE, SCSI, or Fiber Channel to the protocols that the device stores. active physical storage. The host communication protocol is implemented by an IC on the expansion board or motherboard, which is responsible for converting the host bus protocol and the IDE and SCSI storage protocols. For example, in a PC, the IDE protocol functionality is present on the motherboard, and the IDE disk controller has the IDE protocol. Thus, the IDE disk can be connected to the PC’s IDE connector. If the disk only supports SCSI protocols, it is not possible to connect these disks directly to the PC. You need to insert the SCSI card into the PC’s expansion slot and the SCSI disk can be connected to the card. SCSI cards allow the conversion of the PC bus to SCSI. This type of SCSI card realizes the function of the master bus adapter card. If the disk only supports Fiber Channel protocols, then the Fiber Channel protocol is required on the server because the high-speed characteristics of the Fiber Channel are not supported by the generic host card and requires a controller card. dedicated master bus assembly. Once the server is plugged into the host bus adapter card, it can be connected to a Fiber Channel compatible disk.
The host bus adapter card internally has a small processor, memory as a data buffer, and interconnects the fiber and bus channel interconnect devices. This small central processor is responsible for converting PCI and Fiber Channel protocols. It also has other functions to initialize the server port connected to the Fiber Channel network, support superior

FC network card – commonly known as fiber optic network card, scientific name Fiber Channel HBA. The transport protocol is the Fiber Channel protocol and is usually connected to the Fiber Channel switch via fiber optic cable. The interface type is divided into optical port and electrical port. The optical interface is usually through optical fiber to transmit data, the interface module is usually SFP (2Gb/s transmission rate) and GBIC (1Gb/s), the corresponding interface for SC and LC. The interface type of the electrical interface is usually a DB9 or HSSDC pin. iSCSI Network Adapter – The iSCSI HBA name, iSCSI transport protocol, and interface type are the same as the Ethernet adapter. We say “fiber network card” usually refers to the FC HBA card, plugged into the server, external storage with a fiber optic adapter; and an optical Ethernet card commonly referred to as a “fiber Ethernet card” is also installed on the server, but it is located outside the Ethernet switch with the optical port.