Dedicated Database Nodes in the Junos Space Fabric Overview

Before you add database nodes to the fabric, you must configure a Junos Space Virtual Appliance as a Junos Space node to be added to an existing fabric, by using the Junos Space CLI. You can then use the Junos Space Platform UI to add the node as a dedicated database node to the fabric.

When you add database nodes to the Junos Space fabric, the MySQL database is moved to the primary and secondary database nodes and disabled on the Junos Space active and standby nodes, improving the performance of the Junos Space active node.

Junos Space accesses the database through a database VIP address, which is assigned to the primary database node. You specify the database VIP address when you add the database nodes to the fabric. After you add the database nodes to the Junos Space fabric, Junos Space Platform automatically reconfigures the Junos Space server to use the new database VIP address to access the database

Figure 1 shows database nodes in a fabric comprising five nodes.

Figure 1: Fabric with Database Nodes

In case the primary database node goes down or is deleted, the database VIP address is transferred to the secondary node, which becomes the new primary database node, and any other non-load-balancer node in the fabric can be designated the new secondary database node. If the secondary database node goes down or is deleted, the primary database node retains the database VIP address and you can designate any other non-load-balancer node as the new secondary database node. If there is no other non-load-balancer node in the fabric or you choose not to configure a new secondary database node, database high availability is lost.

When you add database nodes to the fabric, node functions are assigned based on the number and type of nodes that already exist in the fabric.

• Adding database nodes to a fabric with one node—By default, the load-balancer, database server, and application logic node functions are enabled on the first node of the fabric. When you add database nodes to a one-node fabric, you must add the second and third nodes together as dedicated database nodes. The database server functions are moved to the dedicated database nodes from the first node, and the first node no longer provides the database server functions.

  When you have one node of the fabric functioning as the active load-balancer server, and two nodes functioning as the primary and secondary database nodes, the fourth node that you add to the fabric automatically assumes the functions of the standby load-balancer server. All subsequent nodes can have only the application logic.

• Adding database nodes to a fabric with two nodes—When you have two nodes in a fabric, the first node functions as the active load-balancer server and active database server, and the second node functions as the standby load-balancer server and standby database server. You can add the third and fourth nodes as database nodes. The database server functions are moved to the primary and secondary database nodes and disabled on the first and second nodes.

  In this case, after you add the two nodes as database nodes, all additional nodes that you add can have only the application logic.

• Adding database nodes to a fabric with more than two nodes—When you have more than two nodes in a fabric, the first node functions as the active load-balancer server and active database server, and the second node functions as the standby load-balancer server and standby database server. The rest of the nodes can have only the application logic. You can add two other nodes as database nodes. The database server functions are moved to the primary and secondary database nodes and disabled on the first and second nodes.

While adding database nodes, you must consider the following points:

• To add a node as a database node, the node must have enough disk space for the MySQL database, and an additional 100 GB of free disk space.

• In the first instance of adding database nodes to the Junos Space fabric, you must configure both the primary and secondary database nodes. You cannot add a primary database node alone. Database high availability is enabled by default.

• If you have already added the primary and secondary database nodes, you cannot add another database node.

• When you configure the primary and secondary database nodes, you must ensure that both the nodes have similar configuration. That is, if one node is a Junos Space Virtual Appliance, then the other node must also be a Junos Space Virtual Appliance with the same configuration for CPU, memory, disk space and so on.

• Junos Space Platform does not permit you to delete both the primary and secondary database nodes at the same time. You can delete either the primary database node or the secondary database node, but not both nodes.

• After the MySQL database is moved to the dedicated database nodes, you cannot move it back to the Junos Space active and standby nodes.