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fabric switch change

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fabric switch change

Hello sir,
Currently our HP servers are connected to EMC’s through brocade switches .since we have many fabric switches, we are planning to implement a new 32port brocade switch.

If we directly connect all the HP servers and EMC’s to the new 32 port switch and the zoning is done properly, will the hardware path to the LUNS/disk will change?

Any help highly appreciated
Steven E. Protter
Exalted Contributor

Re: fabric switch change


If you get everything right device file names should not change.

It requires attention to detail, and you can't run the system connected to both switches at the same time.

Steven E Protter
Owner of ISN Corporation
Acclaimed Contributor

Re: fabric switch change

"will the hardware path to the LUNS/disk will change?"

Most likely.

The hardware path consists of the switch domain ID, the switch type, the port where the storage connects and finally the array.

New hardware path means new device files, unless you run 11.31.

I would consider to vgexport the VG, change the switch and vgimport them again


if you have at least dual pathes, reduce the "old" path from the VG and extend the new path.

Hope this helps!

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Frequent Advisor

Re: fabric switch change

Page 13 of this document explains the hardware path in relation to the switch / domain id etc...

You should be able to use this to determine which path is to which switch if required.

Re: fabric switch change

Hello Steven,
All our servers are in production and its 24/7.currently our servers are connected to the storage through two fabric switches for multi path and redundancy. Is it safe to remove one switch and connect it to the new 32port switch? Will it affect my production? I am more concerned about the device filenames and path.

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Frequent Advisor

Re: fabric switch change

If you remove one path - the storage will still be accessible via the other path, as long as you do not have a hardware failure (Fibre card, switch etc.) then this should be OK for a short period of time. You are just running a higher level of risk.

The way to do this online (with no outage) is to:

1) vgreduce the disk paths for one path from the volume group.
2) Move the cable for this path to the new switch.
(Be very careful which you move as if you pull out the wrong one - all your storage will disappear)
3) run ioscan -f, insf to find your new path to the disks
4) vgextend the volume groups with your new disk paths.

Then repeat the process for the other SAN connection.

When you have finished you should vgreduce and vgextend the disk paths in the volume groups to ensure that half the primary paths go to one fibre card and half to the other to provide some load balancing.

You should also remove the NO_HW devices in ioscan using rmsf. These will be the disks when visible on the other switch.

When you scan for the new disks your controller number will likely change the c part of c-t-d-

The target (t) and device (d) will most likely stay the same as this is based on the advertised lun on the disk array.

One other thing to confirm with the Storage admin is that your SAN is zoned based on WWN not on port otherwise you may not see the disks when you connect to the new switch.
Prashanth Waugh
Esteemed Contributor

Re: fabric switch change

Hi ,

You have to consider the zoning while changing the switch. If its a soft zoning then it will not create any complexity. But if its a hard zoning then you should be very careful.

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Re: fabric switch change

problem solved .thank you all