Cisco guru and long time networking expert Ivan Pepelnjak hits the nail on its head with the below post. It is one more addition to my series of why you should stay away from FCoE. FCoE is only good for ONE thing: to stay confined in the space of the Cisco UCS platform where Cisco seems to obtain some benefits.
Today I got a question around the option for long-distance replication between enterprise arrays over a FCoE link. If there is ONE thing that I would put towards the HDS arrays is that they are virtually bulletproof with regards to data-replication and 6x6x6 across 3 data-centres replication scenarios in cascaded and multi-target topologies are not uncommon. (yes, read that again and absorb the massive scalability of such environments.)
If however you then start to cripple such environments with a greek trolley from 1000BC (ie FCoE) for getting traffic back and forth you're very much out of luck.
Read the below from Ivan and you'll see why.
ipSpace.net: FCoE between data centers? Forget it!: Was anyone trying to sell you the “wonderful” idea of running FCoE between Data Centers instead of FC-over-DWDM or FCIP? Sounds great ... un...
He also refers to a Cisco whitepaper (a must read if you REALLLYY need to deploy FCoE in your company) which outlines the the technical restrictions from an protocol architectural point of view.
The most important parts are that the limitation is there and Cisco has no plans to solve this. Remember though I referred to Cisco in this article all the other vendors like Brocade and Juniper have the same problem. Its an Ethernet PFC restriction inherent to the PAUSE methodology.
So when taking all this into consideration you have a couple of options.
- Accept business continuity to be less than zero unless the hurricane strikes with a 50 meter diameter. (small chance. :-))
- Use FibreChannel with dark-fibre or DWDM/CWDM infrastructure
- Use FCIP to overcome distances over 100KM