Re: md multipath and failover

["Doug Griswold" <griswld@cio.sc.gov>]

Thanks for the info.  My next question is I have set the link down
timeout in the emulex driver to be 15 seconds but the paths are still
not failing over for 5 minutes.  Is there a way to get the scsi timeouts
down
to 30 seconds?  Can I pass anything to the scsi module at boot?  If I
applied your patch that provides load balancing then I would not have to
worry about this issue since they are both working already we wouldn't
have the timeout issue.  Does your patch pick up on the path once it
becomes available after losing it?  


Thanks for the info.
Doug 


>>> Lars Marowsky-Bree <lmb@suse.de> 09/11/03 03:45 AM >>>
On 2003-09-10T18:55:41,
   Doug Griswold <griswld@cio.sc.gov> said:

> Alright I got md/multipath to failover with 2 emulex hba's on red hat
> advanced server 2.1 kernel version 2.4.9-27enterprise.  My next new
> problem is that it took five minutes to fail over from when I yanked
one
> of the fibre channel cables.   Where could this timeout come from?  I
> have tried several times but each time it takes 5 minutes to failover.

> Also it won't failback.  Any ideas out there.  

The plain md multipath can't do failback automatically. People's opinion
on whether that is a good idea do differ ;-)

The timeout is the time needed until the damn (sorry) Linux Kernel SCSI
layers give up retrying and then pass the error code up to md for
handling. You can maybe try tuning some emulex parameters to fix that.

If you want load balancing for the md multipath, you could try checking
out my patch at ftp://ftp.suse.com/pub/people/lmb/md-mp/ vs 2.4, it adds
some features to md and also makes it quite a bit more robust.


Sincerely,
    Lars Marowsky-Brée <lmb@suse.de>

-- 
High Availability & Clustering		ever tried. ever failed. no
matter.
SuSE Labs				try again. fail again. fail
better.
Research & Development, SuSE Linux AG		-- Samuel Beckett


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