Red Hat

Configuring the Load Balancing Mode

1. Click the host name and choose Operation > Modify.
   Figure 7-46 Modifying the host properties
   

   The information displayed on the GUI may vary slightly with the product version.

2. Set Host Access Mode to Load balancing for both the local and remote storage systems.
   Figure 7-47 Setting the host access mode
   

Configuring the Local Preferred Mode

1. Click the host name and choose Operation > Modify.
   Figure 7-48 Modifying the host properties
   

   The information displayed on the GUI may vary slightly with the product version.

2. For the local storage system, set Host Access Mode to Asymmetric and Preferred Path for HyperMetro to Yes. For the remote storage system, set Host Access Mode to Asymmetric and Preferred Path for HyperMetro to No.
   Figure 7-49 Settings on the local storage system
   
   Figure 7-50 Settings on the remote storage system
   

Installing Multipathing Software

Generally, multipathing software packages in Red Hat are rpm packages starting with device-mapper-multipath. If you did not install the multipathing software when installing the operating system, you can obtain the software package from the system image and use the rpm command to install it.

Modifying the Configuration File

DM-Multipath's most important configuration file is /etc/multipath.conf.

Some operating systems have this file by default. If your operating system does not have this file, you can copy the multipath.conf or multipath.conf.synthetic file to the /etc directory to generate one.

[root@localhost ~]# cp /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf /etc/multipath.conf

If the system does not have a template, run the /sbin/mpathconf --enable command to manually generate /etc/multipath.conf.

If Host Access Mode is set to Load balancing on the storage system, add the following content to the devices field in the /etc/multipath.conf file:

devices {
      device {
               vendor                  "HUAWEI"
               product                 "XSG1"
               path_grouping_policy    multibus
               path_checker            tur
               prio                    const
               path_selector           "round-robin 0"
               failback                immediate
               no_path_retry           15
}
}

If Host Access Mode is set to Asymmetric on the storage system, add the following content to the devices field in the /etc/multipath.conf file:

devices {
      device {
               vendor                  "HUAWEI"
               product                 "XSG1"
               path_grouping_policy    group_by_prio
               path_checker            tur
               prio                    alua
               path_selector           "round-robin 0"
               failback                immediate
               no_path_retry           15
}
}

Starting the Multipathing Software

After configuring the configuration file, run the following command on the host to start the DM-Multipath process on RHEL 6:

/etc/init.d/multipathd start

For RHEL 7 and RHEL 8, run the following command to start the DM-Multipath process:

systemctl start multipathd.service

Setting the Multipathing Software to Run at System Startup

For RHEL 6, run the following command to run the multipathing software at startup:

chkconfig multipathd on

For RHEL 7 and RHEL 8, run the following command:

systemctl enable multipathd.service

Verifying the Load Balancing Mode

Run the multipath -ll command to verify that the configuration has taken effect. In load balancing mode, all paths are active. The following is an example.

[root@localhost ~]# multipath -ll
mpathaf (361603041002d0306003e6dc300000009) dm-9 HUAWEI  ,XSG1            
size=5.0G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 2:0:2:4 sde  8:64   active ready running
  |- 9:0:2:4 sdq  65:0   active ready running
  |- 2:0:3:4 sdaw 67:0   active ready running
  |- 9:0:3:4 sdas 66:192 active ready running
  |- 2:0:0:4 sdi  8:128  active ready running
  |- 9:0:0:4 sdak 66:64  active ready running
  |- 2:0:1:4 sdo  8:224  active ready running
  `- 9:0:1:4 sdao 66:128 active ready running
mpathae (361603041002d0306003e549f00000000) dm-3 HUAWEI  ,XSG1            
size=50G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 2:0:2:1 sdb  8:16   active ready running
  |- 9:0:2:1 sdm  8:192  active ready running
  |- 2:0:3:1 sdat 66:208 active ready running
  |- 9:0:3:1 sdap 66:144 active ready running
  |- 2:0:0:1 sdf  8:80   active ready running
  |- 9:0:0:1 sdah 66:16  active ready running
  |- 2:0:1:1 sdj  8:144  active ready running
  `- 9:0:1:1 sdal 66:80  active ready running

Verifying the Local Preferred Mode

Run the multipath -ll command to verify that the configuration has taken effect. In local preferred mode, status=active corresponds to the preferred paths on the local storage system, and status=enabled corresponds to the non-preferred paths on the remote storage system. The following command output indicates that the configuration has taken effect. Generally, the prio value of a preferred path on a Linux system is 50, and that of a non-preferred path is 10. The following is an example:

[root@localhost ~]# multipath -ll
mpathaf (361603041002d0306003e6dc300000009) dm-9 HUAWEI  ,XSG1            
size=5.0G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| |- 2:0:2:4 sdak 66:64  active ready running
| |- 9:0:2:4 sdba 67:64  active ready running
| |- 2:0:3:4 sdao 66:128 active ready running
| |- 9:0:3:4 sdbe 67:128 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
  |- 2:0:0:4 sdh  8:112  active ready running
  |- 9:0:0:4 sdi  8:128  active ready running
  |- 2:0:1:4 sdp  8:240  active ready running
  |- 9:0:1:4 sdq  65:0   active ready running