ACP uses specific terms to cover different topics that are concerned with keeping data viable during computer failure.
Replacement: If a terminal fails or is destroyed, the session stays active on the terminal server while the thin client is replaced. This is covered in the Replacement article.
Failover: Failover is the ability to switch between multiple terminal servers if a terminal server fails. This is built in to every ThinManager Ready thin client. This is the focus of this article.
Instant Failover: Instant Failover is the ability of ThinManager Ready thin clients to connect and login to two terminal servers simultaneously. This allows applications to be pre-loaded so that a failure to one terminal server causes minimal impact because the terminal will quickly switch to an existing session. This is covered in the Instant Failover article.
Redundancy: Redundancy refers to multiple ThinManager Servers. ThinManager Ready thin clients are not dependent on ThinManager after booting, and will continue to run if the ThinManager Server fails. However, rebooted terminal will wait until the ThinManager Server is restored until it boots and receives its configuration. For this reason some people use a backup, or Redundant ThinManager Server. This is covered in the Redundancy article.
Every ThinManager Ready thin client has the ability to switch between multiple terminal servers if a terminal server fails. Each thin client has a program that monitors its terminal server. If the terminal server fails to respond to the terminal, it will drop the broken connection and connect to a backup terminal server, allowing it to continue to function.
Failover requires:
Simple Failover - Before Failure
This shows a pair of terminal servers, one used as the primary with the terminals connected and running sessions, and a second terminal server as the backup, or secondary terminal server.
Simple Failover, After Failure
This shows the results of a failure of the primary terminal server. The thin clients would detect the failure and switch to the secondary terminal server where they would login and continue running.
Note: This does not synchronize the hard drives. This gives you the ability to continue to run the thin client by connecting to a backup. Data pulled from an outside source like a PLC or file server would be the same on either terminal server.
Failover is configured in the Terminal Configuration Wizard. It is configured differently when using individual terminal servers and Terminal Server Groups.
Terminal Configuration Wizard - Select Individual Servers
If individual terminal servers are to be used, select the Select Individual Terminal Servers radio button on the Terminal Server Selection page.
Terminal Configuration Wizard - Terminal Server Selection
Configure failover on the Terminal Server Selection page by adding two or more terminal servers in the Selected Terminal Servers field Upon bootup, the terminal will connect to the first terminal server in the list, considered the primary terminal server. If the primary fails, the terminal will connect to the next terminal server in the list. The terminal will use all the terminal servers in the list, if needed.
The Enforce Primary Terminal Server Connection checkbox will keep the terminal monitoring the first terminal server in the list, even if it has failed. If the terminal detects that the primary terminal server is back on line, it will drop its connection to the backup and reconnect to the primary terminal server.
Terminal Server Groups allows a terminal to connect to a group of servers. The Terminal Server Group will have Failover within that group if the Terminal Server Group has two or more terminal servers added to it. This is configured in the Terminal Server Group Wizard.
Launch the Terminal Server Group Wizard by selecting ThinManagerServer > Server List Management > Terminal Server Group List from the ThinManager menu. This is detailed in Terminal Server Groups.
Terminal Server Group List
If the Available Groups box is empty, select the Add Group button to launch the Terminal Server Group Wizard.
If the Available Groups box has groups, select the Add Group button to add a new group, or highlight an existing group and select the Edit Group button.
Terminal Server Group Wizard - Terminal Server Group Members
Member terminal servers are added to the group on the Terminal Server Group Members page. Adding two or more terminal servers to the Selected Terminal Servers field will enable failover. The terminal will connect to the terminal servers in the order given, unless the Terminal Server Group is using SmartSession.
Terminal Server Group Wizard - Terminal Server Group Members
As the Terminal Server Group Wizard proceeds, the Group Options page allows the Terminal Server Group to use SmartSession load balancing.
SmartSession uses the CPU usage, Memory usage, and the number of sessions on a terminal to determine its load. Terminals connecting to a Terminal Server Group with SmartSession will ask ThinManager for the load numbers, then will connect too the server with the lightest load, instead of the order listed.
The terminal is configured to use Terminal Server Groups by selecting the Use Terminal Server Groups radio button on the Terminal Server Specification page of the Terminal Configuration Wizard.
Terminal Configuration Wizard -Terminal Server Specification Page
This will allow you to select a Terminal Server Group, or Groups if the Enable MultiSession check box is selected, for the terminal to use.
Terminal Configuration Wizard - Terminal Server Selection Page
The Terminal Server Selection page of the Terminal Configuration Wizard allows the Terminal Server Groups to be selected for the terminal by adding them to the Selected Terminal Server Groups field with the arrow buttons.
(Updated 6/20/2007)