Configuring DM-Multipath

DM-Multipath manages multiple paths between the Linux host and the storage cluster. Configuring DM-Multipath on a LUN, which appears to the Linux host as a SCSI device, enables your Linux host to access its LUN on the storage cluster if a path or component fails.

1. Edit the /etc/multipath.conf file as follows:

   Determine whether there are non-NetApp SCSI devices to exclude (blacklist).

   These are devices that are not displayed when you enter the sanlun lun show command.

   • If there are non-NetApp SCSI devices to exclude, enter the worldwide identifier (WWID) for the devices in the blacklist section of the multipath.conf file.

     To display the WWID of a non-NetApp SCSI device, enter the following command on the device that you want to exclude, where SCSI_device_name is a device that you specify: /lib/udev/scsi_id -gud /dev/SCSI_device_name

     For example, if /dev/sda is the non-NetApp SCSI device that you want to exclude, you would enter the following: /lib/udev/scsi_id -gud /dev/sda

     This displays the WWID of the device, which you can copy and paste in the multipath.conf file.

     Example

     In the following example showing the blacklist section of the multipath.conf file, the non-NetApp SCSI device with WWID 3600508e000000000753250f933cc4606 is excluded:

     blacklist {
                 wwid       3600508e000000000753250f933cc4606
                 devnode    "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
                 devnode    "^hd[a-z]"
                 devnode     "^cciss.*"
     }
     

   • If there are no devices to exclude, remove the wwid line from the multipath.conf file.

2. Start the DM-Multipath daemon: /etc/init.d/multipathd start
3. Add the multipath service to the boot sequence so that the multipath daemon always starts during system boot: chkconfig multipathd on