Geom multipath

My Myself avasek at
Fri Nov 7 01:07:11 PST 2008

Thanks!. I did know that there would be only one active path, but path switching doesnt seem to happen when one path fails. The behaviour is intermittent, so i was wondering if there are any kernel tunables that i could play with, like timeout variables etc.

From: John Nielsen <lists at>
To: freebsd-questions at
Cc: Ganesh kamath <ganbi at>
Sent: Thursday, November 6, 2008 8:36:13 PM
Subject: Re: Geom multipath

On Thursday 06 November 2008 07:13:36 am Ganesh kamath wrote:
> I am trying to get multipath running in freebsd version 7. Are there
> any configuration files that i can tweak with geom multipath?. The
> paths are active/passive to the storage array and i dont seem to have
> control of what path the IO takes, so i was wondering if there are any
> tweaks thati could do to control the flow of IO to a specific path.

Read the manpage. Thoroughly. gmultipath(8). :) There is only one active 
path to any device, and it is the first in the list of devices. You 
specify the device list when you create the provider and it is updated if 
errors occur and when gmultipath labeled devices reappear. I would 
guess/hope that the order would be preserved across a reboot but I'm not 
sure. That type of question might be suitable for the freebsd-geom@ 
mailing list.

> Also, the IO doesnt resume when i try to do some cable pulls and plug
> them back.

If you're not using an mpt or isp disk controller then you have to 
initiate a rescan manually for the device to reappear. See camcontrol 
and/or atacontrol. When the device _does_ reappear it will be inserted at 
the end of the list, so I/O will continue across the alternate path which 
is still first in the list.


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