[dm-devel] Creation of the mpath# devices

[Benjamin Marzinski]

On Thu, Nov 15, 2007 at 03:02:45PM -0600, Scott Moseman wrote:
> I guess my problems are never completely eliminated... :)
> 
> Setup device-mapper multipathing in RHEL 4
> http://kbase.redhat.com/faq/FAQ_51_7170.shtm
> 
> Per the above KB, after the multipath daemon is configured and
> started, "The multipath -v2 command prints out multipathed paths that
> show which devices are multipathed. If the command does not print
> anything out, ensure that all SAN connections are set up properly and
> the system is multipathed."
> 
> # multipath -v2
> 
> I get nothing on my server.  Although here's what I do get.
> 
> # multipath -l
> 30690a018f015191a6472441d1500f057
> [size=4 GB][features="0"][hwhandler="0"]
> \_ round-robin 0 [active]
>  \_ 3:0:0:0 sdc 8:32 [active][ready]
> \_ round-robin 0 [enabled]
>  \_ 1:0:1:0 sdb 8:16 [active][ready]
> 
> # multipath -v3
> --- snipped ---
> #
> # all paths in cache :
> #
> 30690a018f015191a6472441d1500f057  1:0:1:0 sdb 8:16  [active][ready] EQLOGIC /
> 30690a018f015191a6472441d1500f057  3:0:0:0 sdc 8:32  [active][ready] EQLOGIC /
> hda blacklisted
> sda blacklisted
> --- snipped ---
> 
> What am I missing?  As far as I can tell, I'm following the RHEL KB
> perfectly and it's still not working as expected (although now I'm
> much farther than before!).

If you were only expecting to have /dev/sdb and /dev/sdc multipathed,
then you are fine.  The problem is in the Knowledge Base article.

# multipath -v2

only prints out the multipath maps that it creates.  If, as in your
case, the map already exists, it should print nothing.

# multipath -l

prints out all the existing multipath devices.
You should see the device node

/dev/mapper/30690a018f015191a6472441d1500f057

and the symbolic link

/dev/mpath/30690a018f015191a6472441d1500f057

Which you can use to access the device. If you don't like dealing with
such a cumbersome name, you can always add

      user_friendly_names yes

to the defaults section of /etc/multipath.conf

-Ben
 
> Thanks!
> Scott
> 
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