Fibre channel vs. iscsi

January 29, 2016 Neal Terracciano

iSCSI vs. Fibre Channel has been one of the most disputed subjects in storage for at least the last ten years. With both camps firmly planted on opposite sides of the river, it’s almost impossible to get a consensus answer on which standard is better for your business.

The Big Misconceptions

On a high level, Fibre Channel and iSCSI both do the same thing. They encapsulate iSCSI traffic and connect initiators with targets for block storage, essentially fooling a machine into thinking that its disks are local. In order to get a clearer picture, we need to dispel some myths and de-emphasize some of the points that have traditionally dominated this discussion. Here are the biggest misconceptions and red herrings surrounding the iSCSI and Fibre Channel debate.

1. Fibre Channel is lower latency than iSCSI

Science doesn’t lie and the speed of light is constant on earth, so based on physics alone, iSCSI is less efficient than FC. There! I said it. Fibre Channel is theoretically faster than iSCSI and here’s why. iSCSI requires a few more operations than Fibre Channel; and Fibre Channel doesn’t have to share the road with anyone. Here’s the catch: nine times out of ten, this doesn’t matter because the difference is beyond human perception. At the same time, many iSCSI deployments outperform Fibre Channel deployments so we need to stop having this “ My Dad is stronger than your Dad’ discussion” and start asking the right questions.

2. iSCSI has more throughput than Fibre Channel 

I’ll say it again, nine times out of ten; your network will never saturate 8 Gb Fibre Channel, or 10 Gb iSCSI. Very few businesses ever even hit the ceiling on their 1 GB network. Look at your current workload, are you wasting your time on this discussion too? There are cases where this becomes important, but I’ll bet you're one of the nine that won’t be affected by this part of the debate.

3. Fibre Channel is more expensive than iSCSI

I don’t know who started this one, but it stuck. While this may have been the case five or ten years ago, you can now get a pair of Fibre Channel switches for much less than a pair of 10 GB switches. Did you need to upgrade your core? If you didn’t, but needed better switches for iSCSI, guess which option is more expensive now. That’s right, iSCSI.

4. iSCSI is easier to manage than Fibre Channel

This one is undeniably true!  ... IF you have a pristine and underutilized network. If you wouldn’t use the words ‘pristine and underutilized’ to describe your network to an outsider, you better change your assumption here. Think about it... you’re about to introduce the largest workload your network has ever seen.  

Having few or no internal resources for Fiber Channel can be a big concern for a host and storage infrastructure under constant change. However, if little-to-no changes to the hosts or storage are expected, then you may NEVER find yourself logged into a Fibre channel switch. That sounds pretty unproblematic to me.

5. FC is the best and most preferred protocol

What makes iSCSI such a powerful and preferred protocol is the fact that it’s a converged standard. iSCSI can run on any data network as it stands. If you need to upgrade both core and storage, it’s hard to walk away from iSCSI and its associated cost benefits. If you’re constantly adding nodes and workloads, iSCSI can offer some major advantages. If you’re looking to embrace your inner hyperconvergence, native Fibre Channel is not a suitable option.

If you take anything away from this, I hope that you understand how futile this discussion is without context. Similar to our discussion on IOP/s and storage performance, we hope that you walk away with a better perspective on which technologies might be best-suited for your environment.

Now that you know the difference between Fibre Channel and iSCSI, learn how redundancy and resiliency differ.

Don't click away yet. Check out my video about the origins of the IOP.
The Origins of the IOP


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