Configuring Multipath in Centos 7 for ISCSI storage LUNS

Install Packages

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

Starting and Enabling the Service 

systemctl start iscsi;
systemctl start iscsid ;
systemctl start multipathd ;

systemctl enable iscsi ;
systemctl enable iscsid ;
systemctl enable multipathd ;

Discovering the iSCSI Targets
iscsiadm -m discovery -t sendtargets -p 10.1.1.100
iscsiadm -m discovery -t sendtargets -p 10.1.0.100


Login to all the targets
iscsiadm -m node -l

Configure basic Multipath  on both Server’s(controller/Controller2)

mpathconf --enable --with_multipathd y

cat /etc/multipath.conf

defaults {
 polling_interval        10
 path_selector           "round-robin 0"
 path_grouping_policy    multibus
 path_checker            readsector0
 rr_min_io               100
 max_fds                 8192
 rr_weight               priorities
 failback                immediate
 no_path_retry           fail
 user_friendly_names     yes
}



[root@controller ~]# multipath -ll
mpathb (36a4badb00053ae7f00001c1c54767520) dm-3 DELL    ,MD3000i
size=2.0G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=6 status=active
| |- 13:0:0:1 sdi 8:128 active ready running
| `- 14:0:0:1 sdh 8:112 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  |- 11:0:0:1 sdg 8:96  active ghost running
  `- 12:0:0:1 sdf 8:80  active ghost running
maptha (36a4badb00053ae7f0000181654753fe5) dm-4 DELL    ,MD3000i
size=250G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=6 status=active
| |- 13:0:0:0 sdd 8:48  active ready running
| `- 14:0:0:0 sde 8:64  active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  |- 12:0:0:0 sdb 8:16  active ghost running
  `- 11:0:0:0 sdc 8:32  active ghost running
[root@controller ~]#

Adding Target partition to multipath

Adding Multipath Alias for the Iscsi LUNs in /etc/multipath.conf

multipaths {
        multipath {
                wwid                    36a4badb00053ae7f0000181654753fe5
alias                   LUN0
        }
        multipath {
                wwid                     36a4badb00053ae7f00001c1c54767520
alias                   LUN1
        }
}

[root@controller ~]# systemctl restart multipathd

[root@controller ~]# multipath -ll
LUN1 (36a4badb00053ae7f00001c1c54767520) dm-3 DELL    ,MD3000i
size=2.0G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=6 status=active
| |- 13:0:0:1 sdi 8:128 active ready running
| `- 14:0:0:1 sdh 8:112 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  |- 11:0:0:1 sdg 8:96  active ghost running
  `- 12:0:0:1 sdf 8:80  active ghost running
LUN0 (36a4badb00053ae7f0000181654753fe5) dm-4 DELL    ,MD3000i
size=250G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=6 status=active
| |- 13:0:0:0 sdd 8:48  active ready running
| `- 14:0:0:0 sde 8:64  active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  |- 12:0:0:0 sdb 8:16  active ghost running
  `- 11:0:0:0 sdc 8:32  active ghost running
[root@controller ~]#


 [root@controller ~]# systemctl status multipathd
multipathd.service - Device-Mapper Multipath Device Controller
   Loaded: loaded (/usr/lib/systemd/system/multipathd.service; enabled)
   Active: active (running) since Wed 2014-11-26 06:31:41 EST; 5s ago
  Process: 2920 ExecStart=/sbin/multipathd (code=exited, status=0/SUCCESS)
  Process: 2915 ExecStartPre=/sbin/multipath -A (code=exited, status=0/SUCCESS)
  Process: 2913 ExecStartPre=/sbin/modprobe dm-multipath (code=exited, status=0/SUCCESS)
 Main PID: 2922 (multipathd)
   CGroup: /system.slice/multipathd.service
           └─2922 /sbin/multipathd

Nov 26 06:31:41 controller systemd[1]: PID file /var/run/multipathd/multipathd.pid not readable (yet?)...tart.
Nov 26 06:31:41 controller multipathd[2922]: LUN0: load table [0 524288000 multipath 3 pg_init_retries ...4 1]
Nov 26 06:31:41 controller multipathd[2922]: LUN0: event checker started
Nov 26 06:31:41 controller systemd[1]: Started Device-Mapper Multipath Device Controller.
Nov 26 06:31:41 controller multipathd[2922]: path checkers start up