The facts on Fibre Channel

Although Fibre Channel has been around for a while, it's just now starting to be accepted within the enterprise. As such, there are still many IT pros who don't understand Fibre Channel.

In this article, I'll introduce you to Fibre Channel technology and discuss some of the pros and cons associated with using this high-speed storage solution.

What is Fibre Channel?
Like Ethernet or ATM, Fibre Channel is a networking standard that is designed to move data through specific devices at specific speeds. Fibre Channel is used primarily for server backbones and as a way of attaching a server to a storage device, such as a RAID array or a tape backup device. In fact, Fibre Channel is the architecture of choice for many storage area networks.

One of the primary reasons Fibre Channel is becoming so popular in storage networks is because of its high speed. A basic Fibre Channel implementation can move data at 1.06Gbps. Obviously this speed is significantly faster than the 100Mbps achieved using Ethernet or ATM, which runs at 622Mbps. Gigabit Ethernet is slightly faster at 1.25Gbps, but presently it's possible to scale Fibre Channel implementations in a way that allows the medium to move data at speeds of 2.12Gbps or 4.24Gbps. There's even a 10Gbps solution in the works.

Another factor that helps Fibre Channel move data so quickly is that it uses a larger frame size than comparable technologies. ATM uses a frame size of a mere 53 bytes. Gigabit Ethernet uses a variable-length frame size of between 0 and 1.5 Kb. In comparison, Fibre Channel's frame size varies between 0 and 2 Kb.

Fibre Channel as a storage solution
Fibre Channel is quickly replacing SCSI as the technology used by storage devices such as RAID arrays and tape backup drives. Although Fibre Channel is roughly three times faster than SCSI, there are compatibility issues because some product manufacturers have interpreted Fibre Channel specifications differently from each other. Therefore, until things completely stabilize, it's wise to purchase Fibre Channel products from a common manufacturer rather than mixing and matching brands.

Compatibility issues aside, many IT pros find that Fibre Channel is an answer to their storage prayers. Since a company's data grows daily, each night the system is backing up a little bit more data than the night before. Thus, the window for completing the backup tends to shrink a little bit each year. The only way to back up more data in less time is to get a faster storage device and a faster medium for transmitting the data from the server to the storage device. In production networks, Fibre Channel products have been able to accomplish a sustained transfer rate of 97MB per second when backing up large files. Companies that use Fibre Channel on database servers have reported these servers can handle tens of thousands of I/Os per second due to Fibre Channel technology.

Fibre Channel is ideal as a server backbone because its throughput is perfect for moving large amounts of data. However, there are other reasons for implementing a Fibre Channel backbone that go way beyond mere speed.

One of the largest selling points behind Gigabit Ethernet is that it uses the same frame type as lower speed Ethernet implementations. This means that the servers don't have to perform any type of frame translation when moving packets across the network backbone. Fibre Channel builds on this concept. However, rather than using a common frame type to achieve performance, Fibre Channel is completely protocol-independent from a service transport standpoint. Although Fibre Channel does support the IP and the SCSI protocols, where Fibre Channel really shines is in moving raw data. For example, if Fibre Channel is used to attach a storage device to a server and is also used as a server backbone, then the raw data from the storage device can be moved to the server and then across the server backbone with no regard for protocols.

Another huge advantage to using Fibre Channel as a server backbone is the reliability factor. Fibre Channel supports confirmed delivery of packets. Sure, some protocols support delivery confirmation, but Fibre Channel can perform delivery confirmation at the hardware level for increased performance.

Fibre Channel also fully supports Quality of Service. For anyone who's not familiar with it, Quality of Service is a technology used to guarantee bandwidth to an application. For example, suppose that someone in your organization needed to have a video conference with someone else. As long as the data associated with the video conference passed along the Fibre Channel link, the amount of bandwidth that's necessary for the conference to take place could be guaranteed to the video conferencing software. Even if a big spike in network traffic occurred during transmission, the software would always reserve the requested amount of bandwidth for the video conferencing software.

The flexible solution
Finally, Fibre Channel is designed to be flexible. I already stated that you could use the IP protocol, the SCSI protocol, or no protocol at all. However, other, more obscure protocols, such as the video protocol, are also supported. Just as the protocols that can be used with Fibre Channel are flexible, so too is the physical medium. Fibre Channel is designed to work with either copper wires or with fiber. Although copper is used only for shorter distances, a variety of copper mediums can be used, including telephone wire or coaxial cable. If fiber optic cable is used, distances of about six miles can be achieved with minimal loss of speed.

Fibre Channel is also very flexible in the topologies that it supports. Like ATM and Gigabit Ethernet, Fibre Channel supports switched topologies. However, Fibre Channel also supports point-to-point circuits (as does Gigabit Ethernet) and shared bandwidth loop circuits.

Are you using Fibre Channel in your storage network? TalkBack or send e-mail to us.