[CentOS] Multipath-root (mpath) problems with CentOS 5

Sun Apr 15 17:54:35 UTC 2007
Pasi Kärkkäinen <pasik at iki.fi>

On Sun, Apr 15, 2007 at 05:36:40PM +0000, Finnur Örn Guðmundsson wrote:
> Pasi Kärkkäinen wrote:
> >Hi list!
> >
> >I have a server with dual port Qlogic iSCSI HBA. I set up the same LUN for
> >both ports, and boot the CentOS installer with "linux mpath". 
> >
> >Installer detects multipathing fine, and creates mpath0 device for root 
> >disk.
> >Installation goes fine, and the system boots up and works fine after the
> >install from the multipath root device.
> >
> >After install the setup is like this:
> >
> >LUN 0 on port 1: /dev/sda
> >LUN 0 on port 2: /dev/sdb
> >
> >and those form mpath0 device, which works OK.
> >
> >But then comes the problem.. when I add another LUN for both ports, the
> >setup is like this:
> >
> >LUN 0 on port 1: /dev/sda
> >LUN 1 in port 1: /dev/sdb
> >
> >LUN 0 on port 2: /dev/sdc
> >LUN 1 on port 2: /dev/sdd
> >
> >And now after rebooting the system, root device multipath (mpath0) doesn't
> >work anymore.. initrd seems to use/mount /dev/sda* partitions instead of 
> >mpath0
> >device. In fact the whole mpath0 is not started up.
> >
> >The weird thing is that the other LUN is now using multipathing instead.. 
> >using mpath1 device. 
> >
> >How can I fix that? I'd like to use multipathing for both LUNs, also for 
> >root
> >device.  
> >
> >If I regenerate initrd with verbose flag, it just sets up the mpath1, not
> >mpath0. I guess that's because mpath0 is not running when regenerating
> >initrd. 
> >
> >I have edited /etc/multipath.conf and disabled the "blacklist" line, and
> >added multipath-entries for both LUNs. So those should be fine..
> >
> >Any ideas? 
> >
> >Thanks!
> >
> >  
> There seems to be a bug in the upstream version with mpath & root 
> devices.....I asked RedHat support to help me with a similar problem but 
> go the answer that i should wait until update 1....the current 
> implementation of mpath for boot devices seems to handle adding 
> paths/devices somewhat weird if you add/remove paths....
> 

Thanks for your reply!

Did they have any workarounds? 

-- Pasi

> Bgrds,
> Finnur
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