Tutorial: Add a node to SQL cluster on RHEL

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In this video, I demonstrated how to create a two nodes SQL Cluster instance.

 

I’m going to show you how to add another node to existing SQL Cluster.

 

Topology

 



1.ISCSI target server configuration

 

1.Add the new node (node3) to the ACLs list.

This is the existing setting.

 

 

Here are the commands I used.

 

2. Enable and restart the target service.

systemctl enable target.service

systemctl restart target.service

 

2.ISCSI initiator configuration.

 

Configure ISCSI initiator in the new node (node3)

 

1.Install iscsi-initiator-utils  in all nodes.

sudo yum install iscsi-initiator-utils -y

 

2.Edit the /etc/iscsi/initiatorname.iscsi , replace the existing value with following keywords, the one I used in step 4 of section[ISCSI target server configuration]

InitiatorName=iqn.2020-08.com.contoso:node3

         

 

3.Discover iSCSI disk of the target.

iscsiadm -m discovery -t st -p <ip of iscsi target server>

Here is the command in this tutorial.

iscsiadm -m discovery -t st -p 10.1.0.7

 

 

 

5. (Optional step)After the discovery below database is updated.

ls -l /var/lib/iscsi/nodes

 

6.Make the connection to iscsi target.

iscsiadm --mode node --targetname iqn.2020-08.com.contoso.servers  --login

 

7. (Optional step)After logging in, a session with the iSCSI target is established.

iscsiadm --mode node -P 1

 

8. (Optional step)If you review the messages file, you will see following keywords

sudo grep "Attached SCSI" /var/log/messages

Aug  9 14:38:43 localhost kernel: sd 3:0:1:0: [sdb] Attached SCSI disk

Aug  9 14:38:43 localhost kernel: sd 2:0:0:0: [sda] Attached SCSI disk

Aug 10 02:13:23 localhost kernel: sd 6:0:0:0: [sdc] Attached SCSI disk

 

 

Check the device


 

 

 

 

3.SQL Server configuration.

 

1.Stop SQL Server in the new node(node3)

sudo systemctl stop mssql-server

 

2.Copy the /var/opt/mssql/secrets/machine-key of node1 to node3.

3.Delete the files from the existing SQL Server data directory in node1.

rm -f /var/opt/mssql/data/*

 

4.Configure auto mount to make the OS mount the devices automatically.

1) makeGet the UUID. Please downdown the UUID ,TYPE and directory

blkid /dev/FCIDataVG1/FCIDataLV1

/dev/FCIDataVG1/FCIDataLV1: UUID="727bdb53-d2c3-4799-8fbf-1b138244bc92" TYPE="xfs"

 

2).Edit /etc/fstab to configure auto mount in node3.

Please review this article for more detail

 

 

4.Cluster configuration.

 

1.Edit /etc/hosts to specify the node and ips in node1,node2 and node3.  The hosts files on three nodes should have same setting

 

 

 

2.Create a file to store the SQL Server username and password for the Pacemaker login. Run the following command in node3 (The same login name and password used in node1 and node2)

 

sudo touch /var/opt/mssql/secrets/passwd

sudo echo 'sqlpackmaker' >> /var/opt/mssql/secrets/passwd

sudo echo 'YourStrongP@ssword1' >> /var/opt/mssql/secrets/passwd

sudo chown root:root /var/opt/mssql/secrets/passwd

sudo chmod 600 /var/opt/mssql/secrets/passwd

 

 

3.On both cluster nodes, open the Pacemaker firewall ports. To open these ports with firewalld, run the following command in node 1 and node2

sudo firewall-cmd --permanent --add-service=high-availability

sudo firewall-cmd --reload

 

7.Install Pacemaker packages in node 1 and node2

sudo yum install pacemaker pcs fence-agents-all resource-agents

 

8.Set the password for the default user that is created when installing Pacemaker and Corosync packages. Use the same password in node1,node2 and node3

sudo passwd hacluster

 

9.To allow nodes to rejoin the cluster after the reboot, enable and start pcsd service and Pacemaker. Run the following command in node3

sudo systemctl enable pcsd

sudo systemctl start pcsd

sudo systemctl enable pacemaker

 

 

10.Add the node3 in cluster. Run following commands in active node(node1 in this case)

sudo pcs host auth  node3

sudo pcs cluster node add node3

sudo pcs cluster start --all

sudo pcs cluster enable --all

 

11. Install the FCI resource agent for SQL Server. Run the following commands in node1 and node2

sudo yum install mssql-server-ha

 

 

Failover

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sudo pcs resource move sqlvirtualname1 <NodeName>

 

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