Re: md multipath and failover

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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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