[rhelv6-list] LVM over dm-multipath

[Tom Sightler]

After playing with RHEL6 in VM's for a few weeks we finally decided to
upgrade one of our existing production systems to RHEL6.  It's an older
system, and relatively non-critical, so we had some downtime with it.
The system is connected to an iSCSI SAN via Qlogic iSCSI HBA's, but we
disconnected those during the install.  We installed RHEL6 and
everything seemed fine so we reconnected the SAN, performed the
multipath config, ran vgscan and the existing LVM volumes were found and
everything seemed great.

However, the problems came up when we rebooted.  The system mounted
everything just fine, including the SAN volumes, however, we noticed
that LVM is connecting directly to first physical disk rather than to
the multipath target.  If we deactivate the LVM and reactive it after
the system boots, then the LVM will be accessed via the multipath
device.  It appears that the RHEL6 boot process is activating LVM prior
to activating multipath.

We've tried several options, and found a reference to what sounded like
the problem in the RHEL6 technical notes which told us to create a new
udev rule, but that didn't seem to change anything.

Has anyone else seen this or is this something strange only in our
environment?  Are we doing something obviously wrong?  Any options on
where to look?

Thanks,
Tom