Fibre Channel (SAN)

Posts: 1
Registered: ‎02-18-2011

Extended Fabric, long distance configuration

Hi all

We are trying to setup a switch to switch connexion through dark fiber. The distance is about 30Km and concerned switchs are DCX and Brocade 5100. On each switch we used a long wave SFP, we configured the buffer credit for it and we enabled the Long Distance Fabric mode (using the configure command...).

Now we connected a server (RHEL5.4) to the DCX and a storage array (IBM DS 5300) to the Brocade 5100. We want to provide a storage capacity to the server (some LUNs). The storage array can see the HBA of server and the zoning was correctly done. When the servers scan for detecting new devices it can see the volumes. Until this step every thing seems to be fine.

The problem appers when we try to format the distant LUN : Server hangs after a little time of beginning format command.

We tried then to access a formated LUN. Now server can write data for a short time and after that it hangs. It seems like one parameter was not well configured but we have no idea what can be this parameter...

I want to ask if someone implemented this configuration before (using extended fabric to present distant LUNs) ? Is it possible to do this since I've not found an example explaining simular configuration (All extended fabric examples that I found talk about Mirroring solution) ?

Many Thanks

Valued Contributor
Posts: 931
Registered: ‎12-30-2009

Re: Extended Fabric, long distance configuration

I've done this but with a distance of approx 10K one way.

The reason why all examples are a mirrored configuration only, is because of latency issues which can arise when doing long distance.

Anyway, Do you have a similar host on the site where your storage resides?

If so, did you present the same LUN to that host and try a format or other disk access.

If not please do, this would rule out the LUN and leave you with the long distance and host

If you have a different host on the remote site (where your storage is not), did you present the same LUN and try disk access?

If not, the do that as it can rule out your linux host and leave you with Storage and long distance.

Can you present the output of portbuffershow concerning all ports which service the long distance ISL?

Frequent Contributor
Posts: 140
Registered: ‎02-27-2008

Re: Extended Fabric, long distance configuration

Hi medhaithem.snoussi

You can grab a temporary extend fabric OS license from your vendor to throw into your switches and test how things go.



Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: Extended Fabric, long distance configuration

You should run only the portcfglongdistance command on the ISL ports on both ends.

The configure command should not be used any longer. Please change the value back to the original value.

If you have no extended distance lic on both ends use the LE option.

Check if the ports are error free.


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