Host Bus Adapter (HBA) is a tricky issue to cover. I don’t think there is a proper source that explains exactly what the function of an HBA is. From my understanding, the definition of this component arose from different sources combining knowledge into one bowl that eventually gave a sort of definition that some might understand and some won’t understand at all.
Well, I am here to make sense of it all for you and to prepare this one article that will summarize the HBA functionality.
HBA is a component that, as the name implies, connects to the Bus (these days the PCIe) in the host. A host is usually defined as the activator of the procedure, in our case it usually means a server.
The job description of this component is to connect the host to an external piece of hardware, usually a SAN (Storage Area Network), through a switch or any other type of storage out there.
There are a few different types of connections. RJ-45, which is what most know as Ethernet connectivity in 1GbE and 10GbE, is reserved to the NIC and server/network adapters (I will explain those in the future). This leaves the HBA with Fibre Channel and SFP (Small Form-Factor Pluggable) connectivity. There are other connectors such as SCSI but this is obsolete and I wouldn’t want you to bother with it. Let’s focus on what matters these days.
So why is the HBA important? Well, back in the day, like with everything else, the CPU used to be in charge of the data transfer between the hardware devices and it took the CPUs time and effort away from focusing on what really matters – calculations.
With the HBA around, the CPU can focus on its task and the HBA can be In charge of the data transfer and connectivity between the devices.
Let’s get back to the connectivity for now. The most popular connectivity that is associated with the HBA is Fibre Channel. It comes in 4Gb/s, 8Gb/s and the recent and blazing fast 16Gb/s. Fibre Channel is currently the most preferable connectivity for devices but the cost of implementation has led the industry to steer away from Fibre Channel to FCoE (Fibre Channel over Ethernet). SFP converged Network Adapters can accept the FC (Fibre Channel) protocol and the SFP protocol, which also lowers the cost since it’s an Ethernet protocol.
However, the fastest connectivity out there is without doubt IB (Infiniband). With up to 56Gb/s data transfer rate, no one can compete with it. However, due to the lack of competition in this industry IB pricing by Mellanox is pretty steep, even compared to Fibre Channel. This technology is the fastest without any doubt, but also a bit isolated from the mainstream, pushing Fibre Channel back to the spotlight.
To conclude, the HBA is an integral component of almost any infrastructure solution that does not involve Ethernet connectivity. Usually designed for higher speeds that Ethernet cannot supply (10GbE+), not many businesses will implement such an expensive solution. To those who are thinking of moving to FC, IB or FCoE I hope that now you have a better understanding of the necessary components to connect the dots.