Pre-configuring SAN

This article discusses an example of configuring iSCSI on a SAN for external storage and cluster nodes running on AlmaLinux 8. For other operating systems the configuration procedure may be different.

The order of SAN configuration before creating a network LVM storage:

1. Configure the external storage as an iSCSI target.
2. Configure the VMmanager cluster nodes as initiators (iSCSI initiator).
3. Install the LVM2 software on the cluster nodes.

Key terms

• initiator (iSCSI initiator) – the client device that sends the connection request to the target. In this example, VMmanager cluster nodes act as initiators;
• target (iSCSI target) – a program or device that emulates a disk and handles initiator connection requests. The target can be logically divided into LUNs;
• LUN (Logical Unit Number) – a part of the target, the address of the storage device. An equivalent of a disk partition or a separate logical volume;
• TPG (Target Portal Group) – a group of targets united by a common functional feature. As a rule, targets on the same device are combined into one TPG;
• IQN (iSCSI Qualified Name) – the unique identifier of the initiator or target;
• ACL (Access Control List) — this list specifies which initiators can connect to the target and their authentication data.

External storage configuration

Connect to the server via SSH with a superuser account and perform the following steps:

1. Make sure that you are using the latest version of the software packages:

   AlmaLinux

   dnf update

   CODE

   Astra Linux

   apt update

   CODE

2.  Install the target management shell:

   AlmaLinux

   dnf -y install targetcli

   CODE

   Astra Linux

   apt -y install targetcli-fb

   CODE

3. Check the amount of free space on the disk:

   df -hT

   CODE
   

   We recommend that you use a separate partition or a physical disk to create a target.

4. Create a directory for the target. For example, /var/targetdisk01:

   mkdir /var/targetdisk01

   CODE

5.  Launch the targetcli console:

   targetcli

   CODE

6. Create a file for the target:

   cd /backstores/fileio

   CODE

   create <target name> <path> <size> 

   CODE
    Comments to the command

   <target name> — name of the target. For example, targetdisk1.

   <path> — path to the target file. For example, /var/targetdisk01/targetdisk1.img.

   <size> — file size; For example, 5G is for a 5GB file.

7. Set the IQN for the target:

   cd /iscsi

   CODE

   create iqn.<year>-<month>.<reverse domain>:<name> 

   CODE
    Comments to the command

   <year> — current year

   <month> — current month

   <reverse domain> — reverse domain name. For example, for the domain example.com, specify com.example

   <name> — discretionary name

   The response will contain the number of the created TPG.

8. Create a LUN:

   cd <iqn>/<tpg>/luns

   CODE
    Comments to the command

   <iqn> — target IQN. For example, iqn.2020-02.com.example:MyTarget1

   <tpg> — portal group name. For example, tpg1

   create /backstores/fileio/<target name>

   CODE
    Comments to the command

   <target name> — target name set in item 6
   

   The response will contain the number of the created LUN.

9. Configure ACL for the target:

   1. Set the initiator's IQN:

      cd /iscsi/<iqn>/<tpg>/acls

      CODE
       Comments to the command

      <iqn> — target IQN. For example, iqn.2020-02.com.example:MyTarget1

      <tpg> — portal group name. For example, tpg1

      create iqn.<year>-<month>.<reverse domain>:<initiator name> 

      CODE
       Comments to the command

      <year> — current year

      <month> — current month

      <reverse domain> — reverse domain name. For example, for the domain example.com, specify com.example

      <initiator name> — initiator name

   2. Set the user id and the initiator password:

      cd iqn.<year>-<month>.<reverse domain>:<initiator name> 

      CODE

      set auth userid=<id>

      CODE

      set auth password=<pass>

      CODE
       Comments to commands

      <year> — current year

      <reverse domain> — reverse domain name. For example, for the domain example.com, specify com.example

      <initiator name> — initiator name

      <id> — initiator user id. For example, initiator1.

      <pass> — initiator password

   3. Enable authorization for the initiator: 

      set attribute authentication=1

      CODE

10. Make sure that all settings have been successfully created:

    ls /iscsi/

    CODE

    An example of the command output

    o- iscsi .......................................................... [Targets: 1]
      o- iqn.2020-03.com.example:mytarget1 ............................... [TPGs: 1]
        o- tpg1 ............................................. [no-gen-acls, no-auth]
          o- acls ........................................................ [ACLs: 1]
          | o- iqn.2020-03.com.domain>:initiator1 ................. [Mapped LUNs: 1]
          |   o- mapped_lun0 ........................ [lun0 fileio/targetdisk1 (rw)]
          o- luns ........................................................ [LUNs: 1]
          | o- lun0  [fileio/targetdisk1 (/var/targetdisk01/targetdisk1.img) (default_tg_pt_gp)]
          o- portals .................................................. [Portals: 1]
            o- 0.0.0.0:3260 ................................................... [OK]

    CODE

11. To save the settings, exit the targetcli console:

    exit

    CODE

12. Add the target service to the autorun:

    systemctl enable target

    CODE

13.  If you are using firewalld, set the necessary permissions and restart the service:

    firewall-cmd --add-service=iscsi-target --permanent

    CODE

    firewall-cmd --reload

    CODE

Configuration of cluster nodes

Connect to the cluster nodes via SSH with a superuser account and perform the following steps:

1. Install the required software:

   AlmaLinux

   dnf -y install iscsi-initiator-utils

   CODE

   Astra Linux

   apt install -y open-iscsi

   CODE

2. Specify the previously created initiator IQN in the InitiatorName parameter of /etc/iscsi/initiatorname.iscsi file:

   InitiatorName=iqn.<year>-<month>.<reverse domain>:<initiator name>

   CODE
    Comments

   <year> — current year

   <month> — current month

   <reverse domain> — reverse domain name. For example, for the domain example.com, specify com.example

   <initiator name> — initiator name

3. Edit the /etc/iscsi/iscsid.conf file:

   1. Uncomment the strings:

      node.session.auth.authmethod = CHAP
      

      CODE

   2. Uncomment the node.session.auth.username, node.session.auth.password parameters. Specify the user id and password set in the ACL settings for the target:

      node.session.auth.username = <id>
      node.session.auth.password = <pass>
      

      CODE
       Comments

      <id> — initiator user id

      <pass> — initiator password

4. Check access to the target:

   iscsiadm -m discovery -t sendtargets -p <target ip>

   CODE
    Comments to the command

   <target ip> — IP address of the server with target

   An example of a successful execution of command

   192.0.2.123:3260,1
   iqn.2020-02.example.com:MyTarget1

   CODE

5. Connect to the target:

   iscsiadm -m node --login

   CODE

   iscsiadm --mode node --target <target name> --portal <target ip> --logout

   CODE
    Comments to the command

   <target name> — name of the target

   <target ip> — IP address of the server with target

   iscsiadm -m node --login

   CODE

6. Make sure the target is connected as a block device:

   lsblk

   CODE
   

   Обратите внимание!

   To make the connection settings not depend on block device names, you can connect the target via UUID or WWID. See the official Red Hat documentation for details.

Installing the LVM2 software

For VMmanager to be able to connect network LVM storage to the cluster nodes, install the LVM2 software on all nodes:

dnf -y install lvm2

apt install -y lvm2

When you add a storage to VMmanager, the platform will automatically make the necessary settings on the block device: it will create PV and VG.

If VMmanager detects a VG created by other software on the block device when adding storage, the storage will not be connected.

Useful tips

Related topics:

• Pre-configuring SAN
• Connecting a network LVM storage