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

Sun Apr 15 17:08:16 UTC 2007
Pasi Kärkkäinen <pasik at iki.fi>

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!

-- Pasi