Red Hat Knowledgebase

Upgrading to Red Hat Enterprise Linux 3, Update 3 (U3) is a requirement for swtichover to work correctly for Multipath RAID setups.

There were specific changes made to the multipath locking and failover capabilities between Red Hat Enterprise Linux 3, GA kernels (i.e. 2.4.21-4.EL) and latest Red Hat Enterprise Linux 3, U3 kernels (i.e 2.4.21-20.EL).

In addition, to the latest kernel, the mdadm package also needs to be upgraded to the latest release i.e. mdadm-1.5.0-9 (which is available in Update 3).
The latest mdadm package contains a new system daemon, mdmpd, that is actually responsible for bringing dead paths back to life when the physical link has been re-established.

To check for existing kernel release, use the uname command:

$ uname -r

To check the version of existing mdadm package, use the rpm command with the q (query) option:

$ rpm -q mdadm

Also, ensure that the mdmpd daemon is enabled to start on boot, using the chkconfig command:

# chkconfig --levels 2345 mdmpd on

Note: The system can be updated to the most recent errata version available for Red Hat Enterprise Linux 3 via the Red Hat Network (RHN). See additional articles in the Knwoledgebase on how to update your system, but executing the following will download and update available RPMs (including kernel packages) for your RHN channel:

up2date -uf