Intro:
ACP uses specific terms to cover different topics that are concerned with keeping data viable during computer failure.
Replacement: If a thin client 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 covered in the Failover 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 thin client will quickly switch to an existing session. This is the focus of this 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 thin client 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.
Basic failover is built into every ThinManager Ready thin client. Detecting that the primary server is down and connecting to a backup server is usually achieved in 5 to 15 seconds, depending on the monitoring configuration. Once the session is connected, it may take an additional 15-60 seconds to launch and initialize the programs. Instant Failover was developed for people who need the session to switch to another terminal server and start running immediately, without any delays for starting the applications.
When using Instant Failover, the ThinManager Ready thin client starts sessions on two servers at once. The sessions are cascaded on the thin client, with the primary session on top. If the primary terminal server fails, the preexisting secondary session is switched to the forefront.
Instant Failover, Part 1
When a ThinManager Ready thin client using Instant Failover boots, it connects to two terminal servers, logs in, and start sessions.
Instant Failover, Part 2
The thin client cascades both sessions, with the primary in front. You cannot see the secondary session as it it hidden in back. There is a optional hot key toggle available, though.
Instant Failover, Part 3
If the primary server fails, the thin client monitoring program will detect its failure. The thin client will then switch the focus of the window, showing the secondary session. This session is already initialized so the user is able to proceed at once.
Note: Use a Username, Password, and Initial Program to allow the ThinManager Ready thin client to login automatically and start a program so that the background session is immediately ready and not needing a login and program launch.
If the Enforce Primary feature used, the thin client will switch back to the primary once it is back online.
Note: ThinManager Ready thin clients that use instant failover may require 64 MB of memory.
Instant Failover is initiated by the Instant Failover Module if a ThinManager Ready thin client is using individual terminal servers, or is configured as part of Terminal Server Groups if Terminal Server Groups are used.
Instant Failover is initiated by the Instant Failover Module if a ThinManager Ready thin client is using individual terminal servers .
Run the Terminal Configuration Wizard for the terminal or Group that needs instant failover and proceed to the Module Selection page.
>Module Selection Page - Attach Module to Terminal Window
On the Module Selection page of the Terminal Configuration Wizard, select the Add button to launch the Attach Module to Terminal window. Highlight the Instant Failover Module and select OK. This will apply Instant failover to the Group or thin client when it reboots.
The thin client or group will need to connect to two more more terminal servers. This is done on the Terminal Server Selection page of the Terminal configuration Wizard.
Terminal Configuration Wizard - Terminal Selection Page
Select two or more terminal servers from the Available Terminal Servers list and move them to the Selected Terminal Servers list by highlighting and double clicking, or by using the Arrow buttons.
The thin client will connect to the top two terminal servers in the Select Terminal Server list, with the top terminal server as the primary and the second terminal server as the backup.
If more than two terminal servers are selected, the thin client will connect to the other terminal servers if one of the other terminal servers fail.
Terminal Server Groups allows a thin client to connect to a group of servers. Instant Failover can be applied to this Terminal Server Group in the Terminal Server Group Wizard.
Launch the Terminal Server Group List Wizard by selecting ThinManagerServer> Server List Management>Terminal Server Group List from the ThinManager menu.
Terminal Server Group List
The Terminal Server Group List will show created Terminal Server Groups. Select the Add Group button to create a new Terminal Server Group or highlight a group and select the Edit Group button to configure an existing group.
Terminal Server Group Wizard - Group Options Page
Select the Instant Failover (requires license) check box on the Group Options page to enables instant failover for the Terminal Server Group.
The Group Options allows the configuration of other Terminal Server Group parameters in addition to the Instant Failover.
SmartSession Group - Normally a ThinManager Ready thin client will connect to the terminal servers in the order listed. If the SmartSession Group check box is selected, the Terminal Server Group will use SmartSession load balancing and send the thin clients to the two terminal servers with the lightest load.
Make group available for MultiSession Configurations -This allows the terminal server group to be available to ThinManager Ready thin clients that use MultiSession to connect to two or more terminal server groups. The session for this group would have Instant Failover functionality.
Application Link Group -This option, AppLink, provides the Initial Program function to Terminal Server Groups. The Initial Program function launches a program instead of the desktop. Closing the program will end the connection and force a reconnection to a session running the application. The session for this group would have Instant Failover functionality in addition to the AppLink function.
Enforce Primary - This allows a ThinManager Ready thin client to connect to its original terminal server if that terminal server has failed and recovered. Enforce Primary is not available with SmartSession.
Each Terminal Server Group needs two or more terminal servers to get Instant Failover to function. This is done on the Terminal Server Group Members page of the Terminal Server Group Wizard.
Terminal Server Group Wizard - Terminal Server Group Members Page
Select two or more terminal servers from the Available Terminal Servers list and move them to the Selected Terminal Servers list by highlighting and double clicking, or by using the Arrow button.
The thin client will connect to the top two terminal servers in the Select Terminal Server list, with the top terminal server as the primary and the second terminal server as the backup, unless SmartSession was chosen on the Group Options page.
If more than two terminal servers are selected, the thin client will connect to the other terminal servers if one of the other terminal servers fail.
Instant Failover can be configured to allow a user to toggle between the two instant failover sessions. This is done differently when using individual terminal servers and Terminal Server Groups.
Instant Failover can be configured in the Instant Failover Module to allow a user to toggle between the two instant failover sessions when the thin client connects to individual terminal servers. Run the Terminal Configuration Wizard for the thin client or Group that needs instant failover and proceed to the Module Selection page.
Terminal Configuration Wizard - Module Selection Page
Highlight the Instant Failover Module and select the Configure... button to launch the Module Properties window.
Modules Properties Window
To enable hot key switching between sessions, highlight the Hot Key Switching parameter, select the Enabled value from the Value drop down and select the Set button.
The hot key combination can be changed by selecting the Hot Key Combination is CTRL+ parameter, changing the key in the Value drop down and selecting the Set button.
Select the Done key when finished, close the wizard, and reboot the thin client.
The thin client will toggle between the instant failover sessions when the configured hot key combination is selected.
Instant Failover can be configured to allow a user to toggle between the two instant failover sessions when the thin client is using Terminal Server Groups. To configure this, run the Terminal Configuration Wizard for the thin client or Group that is using a Terminal Server Group with Instant Failover and proceed to the Terminal Server Group Options page.
Terminal Configuration Wizard - Terminal Server Group Options Page
When a thin client is using Terminal Server Groups, selecting the Enable Instant Failover Hotkeys check box will allow the user to switch between instant failover session using the default CTL + F9 hot key.
The default hot key can be changed by selecting the upper Change Hotkeys button and launching the Select Hotkeys windows.
Select Hotkeys Windows<
The hot keys needed to switch between instant failover sessions on using Terminal Server Groups can be changed on the Select Hotkeys window. Select the Control Key or Alt Key radio button and a function key from the drop down box and select the OK button to accept the changes.
Each ThinManager Ready thin client has a monitoring program that is used to detect the integrity of the connection to the terminal server. The thin client will "ping" the terminal server on a regular basis. It the "pings" fail to get a response from the terminal server, the thin client will end the connection to the terminal server and reinitialize the connection to the next available terminal server that the thin client is configured to use. This monitoring program is managed on the Monitoring Configuration page of the Terminal Configuration Wizard.
Run the Terminal Configuration Wizard for the thin client or Group that needs configuring and proceed to the Monitoring Configuration page.
Terminal Configuration Wizard - Monitoring Configuration
The Monitoring Configuration page allows the rate and frequency of the checking of the thin client to terminal server connection status.
The speed can be set by selecting the Fast, Medium, or Slow radio button, or by selecting the Custom button.
The values for the custom setting include:
Primary Up Delay is an amount of time that the ACP Enabled thin client will wait to reconnect to the primary server. This delay is used (usually 30 to 60 seconds) because the server will respond to a ping before it is ready for thin clients to login. This number is the equal to the Monitor Interval times the Primary Up Delay Multiplier, in seconds.
The Instant Failover Module, used by ThinManager Ready thin clients connected to individual terminal servers, should already be installed with ThinManager. If a new version is released, it will be found in the Download section of the ThinManager web site. The new download will need to be added to the ThinManager server.
Select ThinManagerServer > Modules on the ThinManager menu bar to launch the ThinManager module window.
Select the Install Module... button to launch a file browser window.
Figure 7 - File Browser
Use the file browser to point to the unzipped instant failover module. Highlight the file and select the Open button. This will install the module and add it to the list.
Each ThinManager Ready thin client that is using Instant Failover will require an Instant Failover license. These are available from ACP distributors in Standard quantities (5, 10, and 25 packs) and in unlimited licenses for Enterprise customers.
The instant failover license must be activated before being used. It is activated like other ACP licenses, as described in ACP Licensing.
(Updated 6/20/2007)
