Fibre Channel (SAN)

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Contributor
Posts: 37
Registered: ‎05-19-2009

FC8-48

Has anyone had blocking problems using FC8-48 blades in a DCX, can this problem be sovled by only using 32 ports or less per blade?

External Moderator
Posts: 4,986
Registered: ‎02-23-2004

Re: FC8-48

--->>>...blocking problems....

what kind of problem ?

I've installed TWO week ago a large SAN with TWO DCX full populated with FC8-48 Blade and all work fine.

can you tell me the current FOS Rel is loaded and post errshow output if any is present ?

TechHelp24
Regular Contributor
Posts: 201
Registered: ‎11-24-2009

Re: FC8-48

Hi wduglin,

FC8-48 by design is 3:2 oversubscribed so it's expected to face congestion in some stressful workload tests but the architecture is non-blocking in a sense that frames are not getting stuck because of some other frames rushing through. They're either delivered on time or discarded (which is indicated by disc_c3 error counter).

Hope this helps,

Linar

Contributor
Posts: 37
Registered: ‎05-19-2009

Re: FC8-48

If you are only using 32 of the 48 ports would that reduce the chance of congestion? 

Regular Contributor
Posts: 201
Registered: ‎11-24-2009

Re: FC8-48

Yes this will completely remove congestion on the blade. Keep in mind though that FC8-48 is built with two Condor2 ASICs each serving 24 front-end ports, so you should account for oversubscription on ASIC level, not on blade level.

= First ASIC serves ports 0-7 and 24-39.

= Second  ASIC serves ports 8-23 and 40-47.

Each ASIC has (16) 8Gbps uplink ports to the backplane, so as long as you do not exceed that on the front end you won't have oversubscription at all.

Note that this only resolves congestion issues on the front end side, it doesn't necessarily prevent congestion in the network itself.

Hope this helps,

Linar

Regular Contributor
Posts: 164
Registered: ‎05-11-2011

Re: FC8-48

There is another possibility to use all 48 Ports without having any congestion:

As Linar described, the FC8-48 Blade has two times 24 Front-End Ports.

So you are using for example Ports 0-7, 24-31(first ASIC) and Ports 8-23 (second ASIC) to avoid congestion.

Your unused Ports are  #32-39 and #40-47. This ports have to be F-Ports in this solution.

If you configure Zoning only between Ports #32-39 the traffic will pass only the Front-End-Ports on the ASIC.

There will be no Congestion at all because the Back-End-Ports are not used.

The same you can do with the Ports #40-47.

In addition, if you have a number of Devices connected with less then 8G, congestion will not be happen.

Regards Ralf

Kind Regards
Ralf

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