Fibre Channel (SAN)

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Posts: 1
Registered: ‎11-14-2010

Balancing multiple non-trunked Mcdata ISLs

Hi,  hope someone can share more info on this.

Current setup

Brocade fabric consisting of 2x ED48K

Each switch has 2 single-ISLs - no trunking license

Traffic throughput on both ISLs look very balanced and stable.  No issues.

I believe frames are being sent round-robin since there is no trunking license.

Mcdata fabric consisting of 2x ED140M

Each switch has 2 single-ISLs - no open trunking license

Traffic performance on both ISLs are not balanced, sometimes one ISL link has higher throughput, sometimes the other.

What algorithm does Mcdata use to send frames over?  Is there a way to balance both ISLs so that traffic will be split evenly between them both without buying any open trunking license?

Regards,
Derek

Frequent Contributor
Posts: 104
Registered: ‎07-27-2009

Re: Balancing multiple non-trunked Mcdata ISLs

Very simple.

The 48K are most likely setup with exchange based routing. (check with "aptpolicy --show". Will probably return 3 0)

The Mcdata do not use this and use session based routing meaning that when a particular initiator selects a path to a certain target based on FSPF algorithm it's goinf to send all frames via that path. Only a trunking license will solve that.

Also be aware that on a B-class switch even when you use trunking on FOS 6.2 and up you will see un-even balanced ISL. This is by design so nothing to worrie about.

Hope this helps.

Cheers

E

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