iSCSI Initiator for Linux

Prerequisite:

  • Package iscsi-initiator-utils

  • Package device-mapper-multipath

Installing:

Install the iSCSI initiator and multipath tools:

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

Configuring:

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

    # mpathconf --enable --with_multipathd y

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

    devices {
        device {
                vendor                 "LIO-ORG"
                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
        }
}

  3. Restart the multipathd service:

    # systemctl reload multipathd

iSCSI Discovery and Setup:

  1. If CHAP was setup on the iSCSI gateway, provide a CHAP username and password by updating the /etc/iscsi/iscsid.conf file accordingly.

  2. Discover the target portals:

    # 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

  3. Login to target:

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

Multipath IO Setup:

The multipath daemon (multipathd), will set up devices automatically based on the multipath.conf settings. Running the multipath command show devices setup in a failover configuration with a priority group for each path.

# 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 like you would a normal multipath’d iSCSI disk.