iSCSI Initiator for Linux

Prerequisite:

Package iscsi-initiator-utils
Package device-mapper-multipath

Installing:

Install the iSCSI initiator and multipath tools:

.. prompt:: bash #

yum install iscsi-initiator-utils yum install device-mapper-multipath

Configuring:

#. Create the default /etc/multipath.conf file and enable the multipathd service:

.. prompt:: bash #

  mpathconf --enable --with_multipathd y

#. Add the following to the /etc/multipath.conf file:

   devices {
           device {
                   vendor                 "LIO-ORG"
                   product                "TCMU device"
                   hardware_handler       "1 alua"
                   path_grouping_policy   "failover"
                   path_selector          "queue-length 0"
                   failback               60
                   path_checker           tur
                   prio                   alua
                   prio_args              exclusive_pref_bit
                   fast_io_fail_tmo       25
                   no_path_retry          queue
           }
   }

#. Restart the multipathd service:

.. prompt:: bash #

  systemctl reload multipathd

iSCSI Discovery and Setup:

#. Enable CHAP authentication and provide the initiator CHAP username and password by uncommenting and setting the following options in the /etc/iscsi/iscsid.conf file:

   node.session.auth.authmethod = CHAP
   node.session.auth.username = myusername
   node.session.auth.password = mypassword

If you intend to use mutual (bidirectional) authentication, provide the target CHAP username and password:

   node.session.auth.username_in = mytgtusername
   node.session.auth.password_in = mytgtpassword

#. Discover the target portals:

.. prompt:: bash #

  iscsiadm -m discovery -t st -p 192.168.56.101

   192.168.56.101:3260,1 iqn.2003-01.org.linux-iscsi.rheln1
   192.168.56.102:3260,2 iqn.2003-01.org.linux-iscsi.rheln1

#. Log in to the target:

.. prompt:: bash #

  iscsiadm -m node -T iqn.2003-01.org.linux-iscsi.rheln1 -l

Multipath IO Setup:

#. The multipath daemon (multipathd) uses the multipath.conf settings to set up devices automatically. Running the multipath command shows that the devices have been set up in a failover configuration. Notice that each path has been placed into its own priority group:

.. prompt:: bash #

  multipath -ll

   mpathbt (360014059ca317516a69465c883a29603) dm-1 LIO-ORG ,IBLOCK
   size=1.0G features='0' hwhandler='1 alua' wp=rw
   |-+- policy='queue-length 0' prio=50 status=active
   | `- 28:0:0:1 sde  8:64  active ready running
   `-+- policy='queue-length 0' prio=10 status=enabled
     `- 29:0:0:1 sdc  8:32  active ready running

You should now be able to use the RBD image in the same way that you would use a normal multipath iSCSI disk.

#. Log out of the target:

.. prompt:: bash #

  iscsiadm -m node -T iqn.2003-01.org.linux-iscsi.rheln1 -u