This posting will help you configuring multipathing on RHEL 5.3 for LUNs carved from a NetApp SAN. For this guide I am using a C-Class blade system with QLogic HBA cards.

1) Make sure you have the packages needed by RHEL, otherwise install them.

2) Install QLogic Drivers if needed, or utilize RHEL drivers. In my case I am using HP C-Class blades with Qlogic HBA cards. HP drivers can be found at the HP site, driver is called hp_sansurfer. I am utilizing RHEL built in drivers, but you can install the HP/QLogic drivers as follows:

3) If Qlogic HBA, install the SanSurfer CLI, this is very useful program for doing things with QLogic HBA cards, it can be downloaded at QLogic website, install as follows:

4) Install NetApp Host Utilities Kit, the package is a tar.gz file, you can find it at the now site http://now.netapp.com.

Open it and run the install shell script

5) Once Everything is installed on the host, create the LUN and ZONE it from the NetApp, Brocade(SAN Fabric),Host

6) Once it has been Zoned and mapped correctly, verify if your RHEL host can see it.

7) Utilize NetApp tools to see LUN connectivity

8 ) Utilize NetApp tools to check multipathing, not set yet

Time to configure multipathing

9) Start the multipath daemon

10) Find you WWID, this will be needed in the configuration if you want to alias it.

Comment out the blacklist in the default /etc/multipath.conf, otherwise you will NOT see anything.

11) Now you are ready to configure /etc/multipath.conf

Exclude (blacklist) all the devices that do not correspond to any
LUNs configured on the storage controller and which are mapped to
your Linux host. There are 2 methods:
Block by WWID
Block by devnode
In this case I am blocking by devnode since I am using HP and know my devnode RegEx
Also configure the device and alias(optional).
The full /etc/multipath.conf will look like this:

12) Restart multipath and make sure it starts automatically:

13) Verify multipath is working

14) Now you can access the LUN by using the mapper

15) Format it to your liking and mount it

16 ) If you want it to be persistent after reboots put it on /etc/fstab and make sure multipathd start automatically.

17) If possible reboot to check it mounts correctly after reboots.