====== iSCSI and Multipath ======

  * Install package
<WRAP prewrap center>
<code>
# apt-get install open-iscsi multipath-tools multipath-tools-boot
</code>
</WRAP>
  * Configure iSCSI
<WRAP prewrap center>
<code>
# nano -w /etc/iscsi/iscsid.conf

    node.startup = automatic

# /etc/init.d/open-iscsi restart
</code>
</WRAP>
  * Configure multipath (storage with double controller)
Configure kernel modules required by storage.
<WRAP prewrap center>
<code>
# nano -w /etc/initramfs-tools/modules

     + scsi_dh_alua
     + dm_multipath
     + dm_round_robin
     + scsi_dh_rdac
     + sd_mod

# update-initramfs -v -u -k all
# modprobe scsi_dh_alua
# modprobe dm_multipath
# modprobe dm_round_robin
# modprobe scsi_dh_rdac
# modprobe sd_mod
# /etc/init.d/multipath-tools restart
</code>
</WRAP>
Identify wwid of local disk.
<WRAP prewrap center>
<code>

# /lib/udev/scsi_id --whitelisted --device=/dev/cciss/c0d0
3600508b100104a395355303447480011
# /lib/udev/scsi_id --whitelisted --device=/dev/cciss/c0d1
3600508b100104a395355303447480013
</code>
</WRAP>
Configure multipath blacklist.
<WRAP prewrap center>
<code>
# nano -w /etc/multipath.conf

defaults {
        user_friendly_names     yes
        path_grouping_policy    group_by_prio
        path_checker            rdac
        polling_interval        5
        path_selector           "round-robin 0"
        failback                immediate
        no_path_retry           30
        prio                    rdac
        rr_min_io               100
        #getuid_callout                 "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
        }
blacklist {

                # /lib/udev/scsi_id --whitelisted --device=/dev/cciss/c0d0
                wwid 3600508b100104a395355303447480011
                # /lib/udev/scsi_id --whitelisted --device=/dev/cciss/c0d1
                wwid 3600508b100104a395355303447480013

        }

devices {
        device {
                vendor                  "DELL"
                product                 "MD38xxi"
                hardware_handler        "1 rdac"
                features                "2 pg_init_retries 50"
        }
}

# service multipath-tools restart

</code>
</WRAP>

Connect storage.
<WRAP prewrap center>
<code>
# iscsiadm -m discovery -t st -p 192.168.10.100
# iscsiadm -m node -T iqn.xxxxxx --login
# iscsiadm -m session -P 1

Target: iqn.xxxxxx
        Current Portal: 192.168.10.100:3260,1
        Persistent Portal: 192.168.10.100:3260,1
                **********
                Interface:
                **********
                Iface Name: default
                Iface Transport: tcp
                ...
        Current Portal: 192.168.10.101:3260,2
        Persistent Portal: 192.168.10.101:3260,2
                **********
                Interface:
                **********
                Iface Name: default
                Iface Transport: tcp
                ...

</code>
</WRAP>
WWID discovery
<WRAP prewrap center>
<code>
# lsblk
NAME                MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                   8:0    0   200G  0 disk
└─mpatha            252:3    0   200G  0 mpath
sdb                   8:16   0   200G  0 disk
└─mpatha            252:3    0   200G  0 mpath
...

# /lib/udev/scsi_id --whitelisted --device=/dev/sda
3600a0980005ceb2400000efa5643b840
# /lib/udev/scsi_id --whitelisted --device=/dev/sdb
3600a0980005ceb2400000efa5643b840

</code>
</WRAP>

Configure multipath.
<WRAP prewrap center>
<code>
# nano -w /etc/multipath.conf

defaults {
        user_friendly_names     yes
        path_grouping_policy    group_by_prio
        path_checker            rdac
        polling_interval        5
        path_selector           "round-robin 0"
        failback                immediate
        no_path_retry           30
        prio                    rdac
        rr_min_io               100
        #getuid_callout                 "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
        }
blacklist {

                # /lib/udev/scsi_id --whitelisted --device=/dev/cciss/c0d0
                wwid 3600508b100104a395355303447480011
                # /lib/udev/scsi_id --whitelisted --device=/dev/cciss/c0d1
                wwid 3600508b100104a395355303447480013

        }
multipaths {
        multipath {
                wwid    3600a0980005ceb2400000efa5643b840
                alias   Backup
                }
        }
devices {
        device {
                vendor                  "DELL"
                product                 "MD38xxi"
                hardware_handler        "1 rdac"
                features                "2 pg_init_retries 50"
        }
}

# service multipath-tools restart

# multipath -ll

Backup (3600a0980005ceb2400000efa5643b840) dm-3 DELL,MD38xxi
size=200G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
| `- 4:0:0:0 sdb        8:16   active ready running
`-+- policy='round-robin 0' prio=9 status=enabled
  `- 3:0:0:0 sda        8:0    active ready running


</code>
</WRAP>