Overview

This is a simple example of setting up an environment for those who need to run and test DBMS in an ISCSI Multipath environment.

Method

Example Configuration Environment

ISCSI consists of a Target server that provides storage and an Initiator that receives the storage.

In this example, since multiple paths need to be established on the same disk, two IPs that the Initiator can communicate with the Target must be prepared on the Target.

If you only plan to allocate storage without configuring Multipath, it is possible to prepare the Target with a single IP.

It is also possible to proceed with partitioned volumes instead of preparing the entire single disk as the Target,

but in this document, a simple environment for Multipath setup is used, so a single disk is allocated as a LUN.

ISCSI Target Setup Goals

Disk Preparation Details

Prepare two 20GB disks mounted as /dev/sdc and /dev/sdb respectively.

Install targetcli package for ISCSI Target setup

yum install targetcli -y

Check installation using the targetcli command

targetcli

<targetcli ls command query result screen>

Create Disk Objects

/> /backstores/block create iscsi_disk01 /dev/sdb

/> /backstores/block create iscsi_disk02 /dev/sdc

<Error messages displayed in case of incorrect configuration>

You can verify the addition of disk objects by checking the allocation results with the ls command.

Create IQN

Creating an IQN is the process of making a unique address for the server.

• When creating an IQN, a TPG is created simultaneously.
• TPG stands for Target Portal Group, which is a group of settings that allow initiators to connect to the target.

/iscsi create iqn.2025-10.com.ps1.tibero:server1

You can confirm that the IQN has been assigned by checking the ls results.

Create ACL (Access Control List)

You can specify the list of initiators allowed to access the ISCSI target as an ACL.

Move to tpg1

/> cd /iscsi/iqn.2025-10.com.ps1.tibero:server1/tpg1/

/> acls/ create iqn.2025-10.com.ps1.tibero:client1

Change default portal IP for external access

cd portals
delete 0.0.0.0 3260
create 10.0.10.4 3260
create 10.0.10.5 3260

Create LUN

Create a LUN on the initially created disk objects and map it.

This name will be provided to the target.

/> cd /iscsi/iqn.2025-10.com.ps1.tibero:server1/tpg1/

Create LUN using the created disk objects

cd /iscsi/iqn.2025-10.com.ps1.tibero:server1/tpg1/
luns/ create [created volume object name]

/> /iscsi/iqn.20...:server1/tpg1> luns/ create /backstores/block/iscsi_disk01
/> /iscsi/iqn.20...:server1/tpg1> luns/ create /backstores/block/iscsi_disk02

Check Results

• /dev/sdb → assigned to lun0
• /dev/sdc → assigned to lun1
• Portals 10.0.10.3, 10.0.10.5 confirmed

Storage can now be allocated from the Initiator using the ISCSI Portal IP and IQN.

Initiator (Client) Setup

The following steps are performed on the Initiator server to enable disk allocation.

Install ISCSI initiator package to receive LUN allocation

yum install iscsi-initiator-utils -y

Enable daemon

systemctl enable --now iscsi iscsid

Check IQN specified on the target

 vi /etc/iscsi/initiatorname.iscsi

Edit to the following content

InitiatorName=iqn.2025-10.com.ps1.tibero:client1

Confirm

cat /etc/iscsi/initiatorname.iscsi

Discover target

iscsiadm -m discovery --type sendtargets --portal 10.0.10.3

If necessary, disable firewall

systemctl stop firewalld
systemctl disable firewalld

Login to target

iscsiadm -m node -T iqn.2025-10.com.ps1.tibero:server1 --login

Test two paths (connection confirmation)

iscsiadm -m node -T iqn.2025-10.com.ps1.tibero:server1 -l -p 10.0.10.3

iscsiadm -m node -T iqn.2025-10.com.ps1.tibero:server1 -l -p 10.0.10.5

You can see that the same disk is assigned under different names.

lsscsi

Check iscsi sessions

iscsiadm -m session -o show

Confirm that the WWID values of the two devices are the same (meaning the target devices are essentially the same device)

/lib/udev/scsi_id -g -u -d /dev/sdb

/lib/udev/scsi_id -g -u -d /dev/sdd

Configure Multipath with the Allocated ISCSI Disks

Install multipath package

yum install device-mapper-multipath -y

Verify installation

multipath -ll

Copy and edit the multipath.conf example file to /etc/multipath.conf

cp /usr/share/doc/device-mapper-multipath/multipath.conf /etc/

vi /etc/multipath.conf

We will group sdb and sdd as one multipath and sdc and sde as another multipath.

[root@localhost ~]# /lib/udev/scsi_id -g -u -d /dev/sdb
36001405f455cae7657d4377812f36455
[root@localhost ~]# /lib/udev/scsi_id -g -u -d /dev/sdd
36001405f455cae7657d4377812f36455
[root@localhost ~]# /lib/udev/scsi_id -g -u -d /dev/sdc
3600140541a58a71120e4102a678cb7ae
[root@localhost ~]# /lib/udev/scsi_id -g -u -d /dev/sde
3600140541a58a71120e4102a678cb7ae

On Rocky 9, multipath v0.8.7 is installed, and if a parsing error occurs with wwid "",*

register the entire wwid with a regular expression in the blacklist

If you register in the blacklist by devnode, exceptions cannot be handled by wwid.

devnode blacklist is for exceptions by devnode

wwid blacklist is for exceptions by wwid.

Example configuration

blacklist {
       wwid 26353900f02796769
       devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
       devnode "^hd[a-z]"
}

multipaths {
        multipath {
                wwid    36001405f455cae7657d4377812f36455
                path_grouping_policy    multibus
                failback                manual
                rr_weight               priorities
                no_path_retry           5
        }
        multipath {
                wwid    3600140541a58a71120e4102a678cb7ae
                path_grouping_policy    multibus
                failback                manual
                rr_weight               priorities
                no_path_retry           5
        }
}

When using user_friendly_names - yes, multipath devices are created using names like mpathX.

Start multipath service

service multipathd start

After starting, you can confirm that devices are grouped as multipath by checking lsblk

lsblk

Check multipath

 multipath -ll

Multipath can be confirmed in fdisk

References

[Linux] Device-Mapper multipath detailed settings (multipath.conf parameters)