Wednesday, October 30, 2013

What is Fibre Channel Anyway?

I want to do just a brief summary of Fibre Channel (FC) before we started down the basics path.

First, the name. Fiber Channel vs Fibre Channel. When it was originally developed, it was over an optical cable called fiber. Over time, the protocol has been developed to run over copper cables, so the name was changed to Fibre (British spelling) to remove the image of dependence on the cable. This way, we have fiber cables (optical cables that shoot pew pew lasers) and the FC protocol that can run over both copper and optical cables.  The variations that run over Ethernet or IP are called Fibre Channel over Ethernet (FCoE) and Internet small computer system interface (iSCSI).

"So, why FC in the first place?" That is a good question. There are a few different problems that FC helped to fix. First was an outright storage issue. IT departments were installing servers with local disks. These disks were put into a redundant array of independent disks (RAID) configuration which would allow to redundancy in the disk array. Imagine having to manage hundreds of different servers and each of them having their own RAID configurations and disks to monitor? Second was how to migrate all these local disk to some kind of central storage system reliably? This is where FC came in. We could send the small computer system interface (SCSI) commands that the system would send to the disk and transmit them over a distance to a single array. This would allow IT departments to have more disk storage in a redundant array and just carve out a logical disk (logical unit number or LUN) and present it to the server as a local disk. So now we have a one large pool of storage to manage that has redundancy built into it and can present any size LUN we want to the servers. This allows for huge flexibility when deploying physical machines that have different storage requirements. Need more space? Add in another disk. FC allowed for this "block" level of access through faster speeds then ethernet networks would allow at the time. A few of these concepts are changing as servers become virtual and move from the physical boxes into the "cloud" but it's good to know what came before.

That is a general rundown of what FC does and some storage networking info. I will have a post later that goes into the FC protocol specifically. I also will get another post on some great storage appliances and what kind of features they offer as we move from just storage as an appliance to the software defined storage and software defined data center. These discussions get really exciting as we look at what vendors such as NetApp and Cisco are brining to the data center and the flexibility they bring to the different solutions that we can put together.

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