FAS and V-Series Storage Systems Discussions

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Stack Same Path warning... recabling advice.

I am getting "Stack Same path" warning when running Config Advisor. This is because of the connectivity of the primary and redundant path on four stack of FC shelves  look like this:

1d, 1c

3d, 3c

11b, 11a

4d, 4c

I guess what this means, is if the module (example IOM on port 1 where 1d and 1c) breaks, then I lose the entire stack, am I right? potential loss of data? especially since we are using software base ownership (disk assign)

I plan to recable them, but I want to learn more, but I plan to recable them like these:

1d, 3c

3d, 11a

11b, 4c

4d, 1c

What will be the best approach on recabling them? Total shutdown? anything else need to be done on the OS level?

Thanks,

md

19 REPLIES 19
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Re: Stack Same Path warning... recabling advice.

Keep in mind that most cards (including the onboard ports) have one ASIC chip for two ports, you shouldn't use A&B or C&B ports from the same card on one controller.

You might find easier to cable them using same port such on two different cards, for example 1a/3a, 4a/11a partner could be 1b/3b, 4b/11b. You have a lot of choices.

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Re: Stack Same Path warning... recabling advice.

hi, could you please elaborate on why it is not advisable to use A&B or C&B?

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Re: Stack Same Path warning... recabling advice.

You are looking for the A&B modules of the disk shelf. I don't understand what you mean by C&B.

For example:

PRIMARY  PORT  SECONDARY PORT SHELF BAY

-------- ----  --------- ---- ---------

4a.24.0   B    3a.24.0    A    24    0

4a.24.1   B    3a.24.1    A    24    1

4a.24.2   B    3a.24.2    A    24    2

In this example B module is the primary and A is the secondary.

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Re: Stack Same Path warning... recabling advice.

Hi,

I was just responding to your statement

"you shouldn't use A&B or C&B ports from the same card on one controller.You might find easier to cable them using same port such on two different cards, for example 1a/3a, 4a/11a partner could be 1b/3b, 4b/11b".

I understand the part where you say that  I should use port a on different cards. I thought you were saying that I should not use port 'a' on one card, then port 'c' on another card.

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Re: Stack Same Path warning... recabling advice.

Typo, I meant ports A&B are on one ASIC and ports C&D another ASIC.

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Re: Stack Same Path warning... recabling advice.

thanks for clarifying. I heard that advise somewhere also but not so sure the reason behind it.

If I change the redundanth path, will I need to do anything else or will it be auto-detected without interruption.

Thanks,

md

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Re: Stack Same Path warning... recabling advice.

Once you verify MPHA you should be able to move cables without down time. Do it slowly, one cable at a time then make sure everything is working before moving another cable, storage show disk -p before each move.

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Re: Stack Same Path warning... recabling advice.

Hi,

in your sample above, B module is the primary. What determines between A and B module as to which becomes the primary and the redundant?

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Re: Stack Same Path warning... recabling advice.

I guess I am now confusing the primary and secondary to the cable redundancy. The primary is the module connected to the owner of the disk. is that correct?

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Re: Stack Same Path warning... recabling advice.

Ontap does this automatically. Once you move the fiber ports you will see it change.

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Re: Stack Same Path warning... recabling advice.

I found this link. I am not quite sure if the explanation of the FC multipathing for an HA pair is accurate or just confusing me even more.

http://blog.hernanjlarrea.com.ar/index.php/netapp-cabling-and-hardware-basics/

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Re: Stack Same Path warning... recabling advice.

I know people at NetApp struggled with MPHA at first; the concept is difficult to understand at first, once you have worked with it for a while it will make sense. The link you have is about the best explanation you will find; the diagrams are very good at the end of the article. The old shelves had IN/OUT on the modules; they changed at some point to arrows.

If you send me you layout I might be able to help more. Let me know the type of modules you are using in each stack. We have a lot of equipment onsite, I can send pictures if that helps.

You can always get NetApp PS services to help you with this, I'm sure they will charge for this.

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Re: Stack Same Path warning... recabling advice.

Thank you. I will send you something once I have gathered them. Pretty much here is how I understand it in terms of multipathing for an HA.

Controller 1, connects to:

Channel A, IN port of first shelf of stack

Channel B, OUT port of the last shelf of stack

Controller 2 connects to:

Channel B, IN port of first shelf of stack

Channel A, OUT port of last shelf of stack

Is that correct?

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Re: Stack Same Path warning... recabling advice.

You got it.

I would use the same controller ports, Controller 1 connects to stack 1 A IN on controller port 1a and B out would be port 3a on controller 1. Controller 2 would connect to stack 1 A OUT on 1a and port 3a for B IN on the last shelf of the stack 1. To verify this storage show disk -p on both controllers, during downtime you should be able to pull  module A on shelf 1 stack 1 and both systems should stay up, you will see errors messages after a few minutes. Re-insert the module after a few minutes and check the MPHA again.

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Re: Stack Same Path warning... recabling advice.

Thanks again.  six of our stacks are saying " primary and redundant are on the same path" Just by running show disk -p, I can see that they are either both on A or both on B module. On top of that both cables are connected to the same ASIC on the controller (example: 1a, 1b) So they are two issues it seems. What do you think is the best approach in terms in order in which of these issue I should first? should I separate module connectivity first or the ASIC connectivity?

Thanks,

md

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