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Fibre Channel (SAN)

Occasional Contributor
Posts: 6
Registered: ‎11-10-2010

New counter field pcs_err

We have 8 backend paths from each of a set of switches to a flash array with Load Balancing on the Op/Sys.


3 of  those backend paths on each switch report pcs_err counts around 1000. All other counters are 0 or very low.


I've searched and found nothing about this new counter field except that it is 16GB + only and is for the Physical Coding Sublayer.


So, I am wondering if these counts indicate a physical SAN problem or possibly a storage, switch or HBA configuration problem ?



Valued Contributor
Posts: 559
Registered: ‎03-20-2011

Re: New counter field pcs_err

I'm not sure what's the meaning of this counter. You could ask your Brocade or disk array support about it. But from experience, the problem indicator is the regular or at least periodic growth of the counter. If it doesn't grow - everything is OK.
External Moderator
Posts: 5,313
Registered: ‎02-23-2004

Re: New counter field pcs_err

as per my experience, the pcs_err refert to ITW = Invalid Transmission Word and can occur due a Incoding_in and Incoding_out Violations. Encoding violation occur only at 8G or lower, PCS Violation at 10G or higher speed.

Valued Contributor
Posts: 559
Registered: ‎03-20-2011

Re: New counter field pcs_err

That's interesting, thank you for sharing!

Having this in mind, my recommendation stays the same:
- If the counter is only growing during the initial phase of the link setup, but then doesn't grow during the normal production data transfer, I'd say this is some transitory event and it shouldn't have a lot of concerns.
- If the counter keeps growing further, the issue should be investigated, especially because of this last update from Antonio which links this particular counter to the ITW and/or encoding like conditions - that's serious.

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