Extending SAN - Native FC over DWDM Experiences

Unanswered Question
Oct 1st, 2009

We are in the process of adding a new Data Center which will be geographically located about 60 miles from our existing Data Center, the solution I'm proposing for continuous SAN access and replication is deploying a DWDM solution (Ciena or Cisco) to be able to extend native Fiber Channel to the new Data Center which will provide for an easier and staged migration. My only concern is latency over DWDM for FC since the distance is about 60 miles, does anyone have a real life experience or have been through this type of deployment and can provide me with some feedback, advice, "what to look for" etc, will the distance be an issue using DWDM? I appreciate your responses, thank you.

I have this problem too.
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Tom Randstrom Thu, 10/01/2009 - 08:17

If you haven't already reviewed, you might read the following documents that discuss the FC over DWDM options/solutions.

Storage Networking over a Metro Network


8-Port Enhanced Data Muxponder Card for the Cisco ONS 15454


viyuan700 Thu, 10/01/2009 - 09:37


I dont think any other solution can be faster than SAN over DWDM. As they go over DWDM when distance go over certain distance. Like SFP in switches can go only 70Km i.e 43 miles. Over that distance they either need a telco or DWDM solution

See this link for a SAN experiment is done over 465Km. It will give you some more pointers to look for.


Posting some of the points in that study

"For distances under 120 kilometres, LVM mirroring is suitable. For distances greater

than 120 kilometres, PPRC is better. You can nevertheless use PPRC for short distances to

benefit of the advanced copy service functions like Flash Copy coupled with PPRC for



"Our 465km cable

requires a minimum of 930 buffer credits… (CISCO MDS9000 had only 256 of them). With

256 buffer credits, the maximum distance for a 2 Gb/s link is about 128 km. Data rates will

depend heavily on large data buffers to sustain high bandwidth utilization.



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