Configuring iSCSI (Cross-AZ HA Deployment)

Scenarios

This operation is required only in the cross-AZ HA scenario.

EVS disks cannot be shared across AZs. Therefore, three ECSs are required in the cross-AZ HA scenario. Each ECS is bound to a SCSI disk and iSCSI configuration is required for SBD. SAP S/4HANA and SAP HANA can be deployed on the same ECS. Table 1 lists the ECS specifications.

If SAP S/4HANA is deployed across three AZs, create an ECS in each AZ. If SAP S/4HANA is deployed across two AZs, create an ECS in an AZ and two ECSs in the other AZ. The three ECSs must belong to the same ECS group.

Prerequisites

You have created three ECSs.

Procedure

Software installation

NOTE:

Before installing the software, update the software source. To do so, run the following command:

zypper ar --refresh Software source network address

1. Run the following command to install open-iscsi on the server side (three ECSs):

   zypper in open-iscsi yast2-iscsi-lio-server targetcli

2. Run the following command to install open-iscsi on the client side (SAP S/4HANA node):

   zypper in open-iscsi

Server side configuration

3. Log in to a server side ECS.
4. Run the following commands to configure automatic service startup:

   systemctl enable targetcli

   systemctl enable target

5. Run the following command to create an Iblock device named stonith_bd using the drive letter /dev/sda:

   targetcli /backstores/iblock create stonith_bd /dev/sda

   NOTE:

   /dev/sda is the drive letter of the data disk. Set it based on the actual condition.

6. Query the iSCSI IQN.

   iscsi-iname

   Information similar to the following is displayed:

   iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5

7. Create a target using the queried IQN.

   targetcli /iscsi create Queried IQN

   Information similar to the following is displayed:

   server:~ # targetcli /iscsi create
   Created target iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5.
   Selected TPG Tag 1.
   Created TPG 1.

8. Run the following command to create an LUN:

   targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1/luns create /backstores/iblock/stonith_bd

   Information similar to the following is displayed:

   server:~ # targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1/luns create /backstores/fileio/stonith_bd
   Selected LUN 0.
   Created LUN 0.
   NOTE:

   • iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5 is the ID of iqn, which can be queried by running the targetcli ls command.
   • /backstores/iblock/stonith_bd is the Iblock device created in 5.

9. Run the following command to create a portal:

   targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1/portals create

   Information similar to the following is displayed:

   server:~ # targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1/portals create
   Using default IP port 3260
   Automatically selected IP address 192.168.124.10.
   Created network portal 192.168.124.10:3260.
   NOTE:

   /iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5 is the ID of iqn.

10. Create an ACL.
    1. Run the following command to view the initiatorname.iscsi file and obtain value of InitiatorName:

       cat /etc/iscsi/initiatorname.iscsi

       server:~ #cat /etc/iscsi/initiatorname.iscsi
       InitiatorName=iqn.1996-04.de.suse:01:f3cdb3b6ea6a
    2. Run the following command to create an ACL using the value of InitiatorName:

       targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1/acls create iqn.1996-04.de.suse:01:f3cdb3b6ea6a

       Information similar to the following is displayed:

       server:~ # targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1/acls create iqn.1996-04.de.suse:01:f3cdb3b6ea6a
       Created Node ACL for iqn.1996-04.de.suse:01:f3cdb3b6ea6a
       Created mapped LUN 0.

11. Run the following command to disable the authentication:

    targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1 set attribute authentication=0

    Information similar to the following is displayed:

    server:~ # targetcli /iscsi/iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5/tpg1 set attribute authentication=0
    Parameter authentication is now '0'.

12. Run the following command to save the configuration:

    targetcli saveconfig

    NOTE:

    If an error is reported, locate the error, delete .aslist (), and save the configuration.

13. Log in to the other two ECSs of the server side one by one and repeat 4 to 12 to configure the server side.

Client side configuration

14. Log in to an SAP S/4HANA node (client side) and attach the iSCSI disk of a server side ECS to the SAP S/4HANA node.

    iscsiadm -m discovery -t sendtargets -p 10.0.3.250:3260

    iscsiadm -m node -p 10.0.3.250:3260 --login

    NOTE:

    • 10.0.3.250 is the IP address of the server side ECS and 3260 is the default port number of iSCSI.
    • Attach three iSCSI disks of three server side ECSs to the SAP S/4HANA node.
    • You can run the fdisk -l command to view the newly attached disks.

15. Run the following command to attach iSCSI disks automatically once the SAP S/4HANA node starts:

    iscsiadm -m node -T iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5 -p 10.0.3.250 --op update -n node.startup -v automatic

    NOTE:

    • iqn.2003-01.org.linux-iscsi.scsi-0003.x8664:sn.38370da481a5 is the ID of iqn
    • 10.0.3.250 is the IP address of a server side ECS.

16. Log in to other SAP S/4HANA nodes and repeat 14 and 15 to configure all SAP S/4HANA nodes of the client side.