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Fibre Channel or iSCSI: Does It Matter?

While Fibre Channel provides enterprises with high-speed transfer rates, is the amount it offers a bit overkill?

• By Scott D. Lowe
• 05/16/2014

Fibre Channel storage has long been considered the gold standard when it comes to common technologies to deploy to support an organization's computing environment. This environment consists of storage arrays that are outfitted with Fibre Channel connectivity. These arrays are then connected to a dedicated storage networking environment that is comprised of, surprisingly enough, Fibre Channel switches. At the other end of the connection lie the individual servers, each of which is equipped with a Fibre Channel host bus adapter (HBA), which connects the host systems to the same Fibre Channel switches, handily completing the communications loop.

Fibre Channel infrastructure operates at throughput speeds of 1, 2, 4, 8, 10 and 16GB per second (GB/s). Over the years, speeds have continued to increase as storage performance demands have accelerated. Even faster speeds of 32GB/s and 128GB/s are expected to hit the market in the next couple of years.

For years, Fibre Channel and other storage environments relied solely on spinning disks to store data. These disks can only push so much traffic through the communications fabric and it takes a whole lot of disks to even come close to saturating fast Fibre Channel links. With the rise of solid state storage, though, throughput opportunities are much greater and organizations are leveraging this class of storage at many different points in the storage environment, including right in the array.

When compared to iSCSI, there are certainly some benefits to operating a Fibre Channel environment. Most notably, Fibre Channel is purpose-built to support storage and that's all it does. Fibre Channel environments generally enjoy low latency storage access, at least where the communications fabric is concerned.

iSCSI hit the market in the early/mid-2000s in order to address some of the rising concerns surrounding Fibre Channel: cost and complexity. Fibre Channel HBAs for servers and Fibre Channel switches are not inexpensive hardware devices to procure and this communications fabric alone will add tens of thousands of dollars of cost to a storage purchase. Further, because it's a unique communications fabric, FIbre Channel requires a specialized skill set that can tune the technology and configure it using its own administrative schemes.

There are two primary reasons that iSCSI storage environments hit the market by storm. First, iSCSI uses Ethernet as its underlying communications fabric. Ethernet is a common standard and is already pervasive in the enterprise. Leveraging this technology avoided the need to build teams of people with specialized Fibre Channel skills. Second, because of this reliance on an existing ubiquitous technology, iSCSI is much less expensive than Fibre Channel -- by wide margin. iSCSI uses standard Ethernet switches and cabling and operates at speeds of 1GB/s, 10GB/s, and 40GB/s. Basically, as Ethernet continues to advance, iSCSI advances right along with it.

General thinking used to dictate that Fibre Channel was for the enterprise while iSCSI was for smaller organizations, but that mindset has gone the way of the dodo. Today, even large enterprises are relying on 10GB iSCSI storage connections to meet the needs of even the most demanding workloads. Today's data center Ethernet technologies rival Fibre Channel when it comes to being all but lossless. As such, there is less of an underlying performance differentiation than there used to be in the past.

Reality Strikes
It's easy to compare speeds and feeds and attempt to determine which is faster. But, in reality, it really doesn't matter except for the largest organizations and those organizations that are pushing their storage throughput to the limits. In the real world, the link between the storage and the servers is rarely the point of contention when it comes to performance. Think about this: It's really, really hard to fully saturate even a 1GB/s link, let alone a 10 GB/s or 16 GB/s link. Once you hit that 10 GB/s mark, for most organizations, throughout really doesn't become a top concern.

So, the bottom line is this: Throughout speed is important, but it's rarely the metric that has a negative impact on storage performance.