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Contributor
Posts: 46
Registered: ‎06-04-2012
Accepted Solution

Stuck VC Issues

[ Edited ]

Hi Friends,

 

Recently we had a degraded ports on one of the storage pool (IBM SVC). We logged a call with IBM and Brocade. Brocade confirmed that there were some stuck VC's and asked to execute below commands to release Stuck VC. Switch firmware is v7.3.1. Switches are DCX8510 model and uses ICL ports for ISL connectivity.

 

Stuck VC Condition List.

slot 2 internal port 48       
slot 1 internal port 47       
slot 5 internal ports 26, 128
slot 8 internal ports 16, 129
slot 9 internal port 43   

 

To release credits, creditrecovmode --linkreset slot/blade_port. We have executed these commands.

 

I have few queries;

1) How to check on daily basis, the total number of Stuck VC's(backend and frontend) on a switch (apart from RAS logs)?

2) How to detect which front end port has caused the backend stuck VC, or which front end port mapped to the backend port causing stuck VC?

3) How can we check to how many ports this stuck VC has caused issues?

 

Thanks in advance!

 

 

 

 

 

 

Regular Contributor
Posts: 166
Registered: ‎02-05-2014

Re: Stuck VC Issues

This is rather complex and you don't want to go down that rabbit hole.

 

First make sure that you have the latest firmware installed on that box. That already has measures built in to prevent this from happening. Secondly make sure that your have creditrecovery turned on via the "creditrecovmode" command. This monitors the flow and lack ofcredit on the back-end. If something is not right you will get notified via a RAS event.(Cx-1014/1015/1016/1017)

 

 

Kind regards,
Erwin van Londen
Brocade Distinguished Architect
http://www.erwinvanlonden.net The Fibre Channel blog



Q&A -> https://hackhands.com/elo/


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Contributor
Posts: 46
Registered: ‎06-04-2012

Re: Stuck VC Issues

Thanks Ervin for the reply. One quick question,

- Why there is a prolonged stuck VC (backend) when there is a LR issued after a certain time based on EHT or ED_TOV?

 

Highlighted
Contributor
Posts: 46
Registered: ‎06-04-2012

Re: Stuck VC Issues

hi Ervin,

 

I see its already enabled,

 

FC101_SW1:root> creditrecovmode --show
Internal port credit recovery is Enabled with LrOnly
LR threshold (not currently activated): 2
Fault Option (not currently activated): EDGEBLADE
C2 FE Complete Credit Loss Detection is Disabled

 

Regular Contributor
Posts: 166
Registered: ‎02-05-2014

Re: Stuck VC Issues

Depending on the platform a back-end link may be a trunk. If that is the case one trunk-member may still pass traffic and as such will not be flagged as a stuck VC. As such the back-end link-reset may not trigger.

 

Only a few OEM's and Brocade are able to determine that. It is too complex to explain here plus I might betrodding on some Broadcom IP here.

 

Condor 3 and 4 ASIC have improved logic so chances of happening this over there is less.

Kind regards,
Erwin van Londen
Brocade Distinguished Architect
http://www.erwinvanlonden.net The Fibre Channel blog



Q&A -> https://hackhands.com/elo/


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