4.6. Clusters
Once you have configured the services that the cluster will run and the systems that will serve various roles in the cluster, you are ready to set up the cluster itself. Each cluster is defined by an IP address that it manages and redirects traffic for. While most Turbolinux Cluster LoadBalancer 10 installations will have only one of these virtual IP addresses, it is also possible to manage multiple cluster addresses.
The cluster's IP address is also called the virtual server address, because it appears to the outside to be a single server, while actually consisting of several systems. It is considered "virtual" because the IP address used is in addition to the actual IP addresses of each system in the cluster.
To set up your cluster, select `Virtual Servers' from the tlclbconfig main menu. Then continue with the following procedures.
The `Virtual Servers' menu lists all the virtual servers that have been configured. If you do not have virtual IPs configured initially, you will not see a list in the window. Here you also have the familiar `Add', `Edit', and `Remove' buttons.
To add a virtual IP address for the cluster, click `Add'.
Here you enter the information required to configure the virtual server. The information requested is as follows:
Enter the IP address or hostname for the virtual IP address in the `Virtual hostname or IP' field. This is the IP address that will be used when accessing the cluster from the outside. Like all addresses, it must resolve both backward and forward.
Enter your email address in the `Send e-mail alerts to' field. Alerts will be sent whenever an ATM, server node, or service goes down, or if some other fatal event occurs. If you leave this field blank, no email messages will be sent, and you won't know when something goes wrong with the cluster, unless you check the log files.
Choose the `Server pool name' from the list. This is the group of servers that you defined earlier in the `Server Groups' section.
Click `OK' when you have entered the appropriate information for the cluster.
Click `Done' after you have configured all the virtual IP addresses for the clusters. (Normally you will just have the one virtual server.)
You have now successfully configured the cluster. Next, you must define a few parameters that are global to all clusters.
 | Postfix is the standard MTA used on Turbolinux 10 Server. In order for an ATM configured as a cluster node to send alert messages, it must be running the Postfix server services.
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