[dm-devel] Failover between two paths to one LU doesn't work onlinux-iscsi

[Dave Wysochanski]

On Wed, 2006-10-18 at 20:55 +0200, Michael Lyulko wrote:
> >>
> >> 1. How can I configure the DM to automatically detect that a path is 
> >> active again?
> >>     
> >
> > you probably want "failback immediate"
> > there's also been some bugs with failback - not sure about your version
> > - your mileage may vary
> >
> >   
> "failback immediate" didn't help on both SLES9 sp3 and SLES10. The 
> device mapper doesn't
> rescan automatically the paths, so when the failed path is back to life, 
> it is still "failed"
> in multipath -l output.
> Issuing "multipath -p failover" helps to return the path back to 
> "active". I need an automatic "rescan".

This is supposed to be multipathd's job - it's supposed to have a path
checker thread that repeatedly scans and notifies the kernel to
reinstate paths.  If the first state remains "[failed]", it indicates
either multipathd isn't running or it's not notifying the kernel
correctly of the reinstated paths.

I seem to recall there was a sequencing problem - at least on SLES9 SP?
with boot.multipath, multipathd and iscsi - something like multipathd
starting too early, which caused it not to monitor paths properly.  Did
you try restarting multipathd after everything is up (on SLES9)?