Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Planning and Documenting an HA Cluster
Hardware Planning
Chapter 4 99
NOTE Multipath capabilities are supported by FibreChannel HBA device
drivers. Check with the storage device documentation for details. See
also “Multipath for Storage” on page 99.
On the worksheet, enter the names of the device files that correspond to
each LUN for the Fibre-Channel-attached storage unit.
Multipath for Storage
The method for achieving a multipath solution is dependent on the
storage sub-system attached to the cluster and the Host Bus Adapters
(HBAs) in the servers. Please check the documentation that accompanied
your storage sub-system and HBA.
For fibre-channel-attached storage, the multipath function within the
HBA driver should be used, if it is supported by HP. For the QLogic
driver, see “Using the QLogic HBA driver for single-path or multipath
failover mode on Linux systems application note”, which you can find by
entering the terms qlogic multipath application into the search box
of www.hp.com.
The multiple device driver (md) is not supported for fiber channel-based
storage systems. It is supported with Serviceguard and MSA 500 family
devices that support multipath.
md multipath devices cannot be activated via the Serviceguard package
control script. Instead, for multipath only, md activation should be done
at system boot.
The following example creates a multipath device where the two devices
are /dev/sdf1 and /dev/sdh1:
mdadm –create /dev/md0 -level=multipath -raid-devices=2
/dev/sdf1 /dev/sdh1
The command to activate /dev/md0 would be:
mdadm –assemble –scan /dev/md0
This command can be added to the sysinit file.
The above is a simple example. Refer to the mdadm man page for more
information. There is also a “how-to” document whose location on the
internet at the time this manual was published was:
http://tldp.org/HOWTO/Software-RAID-HOWTO.html.