[dm-devel] Re: multipathd: sdc: readsector0 checker reports path is down

[Ray Van Dolson <rvandolson esri com>]

On Thu, Jan 08, 2009 at 11:58:52AM -0800, Chandra Seetharaman wrote:
> 
> 
> On Thu, 2009-01-08 at 11:31 -0800, Ray Van Dolson wrote:
> > I'm still getting the hang of iSCSI and multipath, so bear with me if
> > this is a FAQ that I've missed...
> > 
> > I have a host attaching to an MD3000i via iSCSI/dm-multipath that is
> > working but showing a lot of the following errors in syslog:
> > 
> >   multipathd: sdc: readsector0 checker reports path is down
> you should be using the rdac path checker. In addition to that you
> should be using rdac hardware handler and tpc priority checker.
> 
> If you have and entry for your MD3000i in /etc/multipath.conf, replace
> it with this. If not add this
> -------------------
> devices {
>         device {
>                 vendor                  "DELL"
>                 product                 "MD3000i"
>                 hardware_handler        "1 rdac"
>                 path_checker            rdac
>                 failback                immediate
>                 path_grouping_policy    group_by_prio
>                 no_path_retry           queue
>                 prio_callout            "/sbin/mpath_prio_tpc /dev/%n"
>         }
> }
> ---------------------
> 
> After this change you have to do:
> - multipath -F
> - service multipathd restart
> 
> Let me know how it goes.

This appears to have done the trick.  So, I guess the default path
checker is readsector0 and rdac is another method -- I imagine it
directly talks to my MD3000i to determine path status?

> > 
> > My initial impression is that sdc is likely the "passive" path (for
> > failover) whereas sdd is my active path:
> 
> yes.

Thanks much!

Ray