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Fibre Channel (SAN)

New Contributor
Posts: 2
Registered: ‎06-01-2017
Accepted Solution

More detail about fabric rebuild

Hi all, many thanks for reading my questions:


i have 3 san switches A, B, C; connected together as a fabric, only switch C has connected devices and the switch B is the principal one, so my questions are:


1. If i remove the switch A from the fabric (A is connected with B via E_port), will it trigger fabric rebuild event?

2. I already knew that if i set C as the principal switch by typing "fabricprincipal -p 1" and then remove B from the fabric, it will trigger a fabric rebuild event and after that, C will be the principal one, but is there a more detail log about this event? how can i get it?

3. During the fabric rebuild, are all of the data links between hosts and storage devices disrupted? And how long does it take?

4. Is there a technical documentation about fabric rebuild?




Broadcom Moderator
Posts: 467
Registered: ‎03-29-2011

Re: More detail about fabric rebuild

Hi Long,


Some details are covered in the following document


During the 5-15 second of the BF (Build Fabric) the traffic is not interrupted if it does not pass via switch A.

Only traffic which is passing an ISL(s) or switch which is taken offline is impacted, no other traffic.


For the fabricprincipal, you could in fact move the principal by on switch C by forcing a build fabric before removing the switch


fabricprincipal -p 1 -f


which will not impact traffic at all (see attached article). Notice that then removing the switch A, you only have to deal

with the change in topology - no real traffic is going over the ISL between B and A, only switch related, I assume.


Further, I assume that iod is disable (iodset), and lossless is enabled - that is pending your switch hardware and FOS version.


To summarize:


1. yes, a BF will occur

2. look at the fabriclog CLI (fabriclog -s) on switch B and the new principal (switch C)

3. During a BF traffic is flowing (see referenced paper).  Only effect are on link taken down and potentially caused by iod setting





If this provided you with a solution to this issue, please mark it with the button at the bottom "Accept as solution".

Any and all information provided by me is not reviewed, approved or endorsed by Brocade and is provided solely as a convenience for Brocade customers. All systems and all networks are different and unique. If you have a service affecting network problem, please open a TAC service request for service through Brocade, or through your OEM equipment provider. If this provided you with a solution to this issue, please mark it with the button at the bottom "Accept as solution"
New Contributor
Posts: 2
Registered: ‎06-01-2017

Re: More detail about fabric rebuild

Thank you for answering my questions, that helped me a lot!




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