COMSTAR and Linux Multipathing

COMSTAR and Linux Multipathing

Actually there is nothing COMSTAR specific that is needed to setup Multipathing on Linux when talking to a COMSTAR based target.

There is no need to install device-mapper-multipath package as it has been installed by default on RHL5. In case if you don't have this package then you need to install it.

1. Ensure that Linux client discovers the COMSTAR LUs using command /proc/scsi/scsi.

    [root@trips etc]# more /proc/scsi/scsi
    Attached devices:
    Host: scsi0 Channel: 00 Id: 00 Lun: 00
     Vendor: SUN      Model: COMSTAR          Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 05

2. Comment out the blacklist section from the /etc/multipath.conf.

    #blacklist {
    #        devnode "*"
    #} 

3. Ensure that the following lines are there in /etc/multipath.conf file.

     defaults {
            user_friendly_names yes
            polling_interval 5
            failback immediate
}

4. Start the multipath daemon.

    [root@trips etc]# chkconfig multipathd on
    [root@trips etc]# service multipathd start
    Starting multipathd daemon:
    [root@trips etc]#

5. Load the dm_multipath module

    [root@trips etc]# modprobe dm_multipath
    [root@trips etc]# 

6. Creates and updates the devmaps

    [root@trips etc]# multipath

COMSTAR LUNs can now be seen using command "multipath -ll"