Redundancy

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 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 the focus of this article.

Redundancy

Redundancy Modes Redundancy Requirements Redundant Licenses Synchronization of Configuration IP Configuration of Terminal

ThinManager Ready thin clients need to connect to a ThinManager Server to receive its firmware and configuration as part of the boot process. If the ThinManager Server fails, the ThinManager Ready thin clients will continue to run as they are not dependent on ThinManager.

If these thin clients are rebooted while the ThinManager Server is down, however, the thin clients will be unable to download the firmware and configuration, and will wait until the ThinManager Server is restored before proceeding.

Because of this, using a second redundant ThinManager Server is a common form of insurance. There are 3 types of redundancy.

• Single ThinManager Server (No Redundancy)- If a system has a single ThinManager Server all the terminals will boot from that computer, receive their configuration, then connect to the assigned terminal servers. If the ThinManager Server fails the terminals will continue to function as designed. If they reboot, however, they will be unable to connect to the failed ThinManager Server and will not receive their configuration or connect to a terminal server.
• Fully Redundant ThinManager Servers - If the system has two ThinManager Servers that are synchronized with the same configuration the thin clients can be configured to point to either ThinManager Server to receive their configuration. If the first ThinManager Server has failed a rebooted thin client can connect to the backup ThinManager Server and receive the proper configuration and connect to the proper terminal servers.
  Redundancy requires an identical license set on both ThinManager Servers. Each ThinManager Server is fully functional and can be used to change or configure the thin clients.
• Mirrored Redundancy is a new feature that allows a pair of ThinManager Server to be synchronized with the same configuration so the thin clients can receive their configuration from the backup if it goes down. Mirrored redundancy is less expensive than full redundancy but mirrored redundancy installs the second ThinManager Server as a headless server. It doesn’t allow changes to be made to the configuration except from the primary ThinManager Server. If the primary ThinManager Server fails the thin clients can boot from the secondary ThinManager Server but the configuration cannot be changed until the primary ThinManager Server is returned to service.

Note: All Enterprise licenses include Redundancy.

Redundancy Modes

Single ThinManager Server - No Redundancy

• Least expensive.
• If the ThinManager Server fails the thin clients cannot retrieve their configuration until the ThinManager Server is restored.

Full Redundancy - Two ThinManager Servers

• If a ThinManager Server fails, the other ThinManager Server will provide configuration.
• The ThinManager configuration can be changed on either ThinManager Server at anytime.
• Most expensive as it requires a duplicate set of licenses on the backup ThinManager Server.

Mirrored Redundancy- Two ThinManager Servers

• Provides redundancy at a lower cost than full redundancy.
• Configuration changes can be made only on the primary ThinManager Server. If it fails the thin clients are able to retrieve their configuration but configuration changes must wait until the primary ThinManager is restored.

Redundancy Requirements:

• Two or more ThinManager Servers
• ThinManager licenses on each ThinManager Server. See Redundant Licenses in this article.
• Identical configurations on each, easily achieved with automatic synchronization or the Synchronization tool as explained later in the article.
• Configuring the ThinManager Ready thin clients to boot from the two ThinManager Servers. See IP Configuration later in the article.

Terminal Server Failover with Redundant ThinManager Servers

Redundancy uses two ThinManager Servers. Most systems that use redundancy also provide for failover by using multiple terminal servers. ThinManager do not need to be installed on terminal servers, but can be installed on any Windows computer, NT 4.0 workstation SP5 and greater.

Redundant Licenses

ThinManager needs Terminal Connection licenses to allow the ThinManager Ready thin clients to boot. Other licenses like Instant Failover, WinTMC, and Share Keyboard and Mouse may also be used.

In a redundant system each ThinManager Server needs its own set of licenses so that the the thin clients can receive licenses regardless of which ThinManager Server it boots from. See ACP Licensing for details on the license process.

Mirrored Licensing is another method of acheiving redundancy. See Mirrored ThinManager Servers for details.

Synchronization of ThinManager Server Configuration

If multiple ThinManager Servers are used, their configurations should be identical so that it thin clients will receive the same configuration regardless of which ThinManager Server the terminal boots from. There are two ways to synchronize, automatically or manually.

See Synchronization for details.

Automatic Synchronization

hinManager has an automatic synchronization tool that makes it easier to keep the configuration on two ThinManager Servers the same. Changing a configuration on one will make the change on the other. Automatic Synchronization has a few things to consider:

• It is a good idea to backup the configuration before making changes because a mistake on one ThinManager Server will pass the mistake to the other ThinManager Server. The backup will allow a chance to restore the configuration to a pre-mistake state.
  ThinManager 3.1 has a scheduling function that can be set to automatically back up the configuration. See Scheduling for details.
• Automatic synchronization is required for Mirrored Redundancy. See Mirrored Redundancy.
• Automatic synchronization will configure each thin client to send the green/red status lights to both ThinManager Servers so the ThinManager Server Monitor List page isn't shown in the Terminal Configuration Wizard, as it ism’t needed.

Automatic synchronization is configured on the ThinManager Server List Wizard. Launch it by selecting Manage > ThinManager Server List ThinManager menu. Proceed the ThinManager Server List page.

ThinManager Server List Wizard

Selecting Add Server will launch a ThinManager Server Definition window that allows the entry of the ThinManager Server name and IP address.

ThinManager Server Definition

Entering the network name of the ThinManager Server and its IP address allows the ThinManager Servers to be tied to a convenient name without the need of a DNS server.
Enter the computer name as found in the Microsoft System Properties in the ThinManager Server field. Add the IP address of the ThinManager Server in the ThinManager Server Address field, and select OK. This adds the ThinManager Server to the ThinManager Server list.
Discover will find and fill in the IP address for a ThinManager Server entered in the ThinManager Server field.

ThinManager Server List

Enter two ThinManager Servers into the ThinManager Server List to set up automatic synchronization.
Select the Automatic ThinManager Server Synchronization checkbox once two ThinManager Servers are added. When this is checked, the Add Server button will become inactive and no more ThinManager Servers can be added.
Select Finish to close the ThinManager Server List wizard.
The two ThinManagers will now be synchronized. The synchronization status can be checked on the Synchronization tab of ThinManager.

Properties Tab

The Properties tab will show whether the ThinManager Server is the master or the slave (although it doesn't matter which is which), the synchronization state, and the IP address of the synchronized partner.

Manual Synchronization

The Synchronized Configuration wizard is the tool that synchronizes multiple ThinManager Servers. Select Manage> Synchronize Configuration in ThinManager 3.x or select ThinManagerServer> Synchronize Configuration from the ThinManager menu of older versions tol launch the ThinManager Server Configuration Synchronization Wizard.

Synchronize ThinManager Server Configuration Wizard

The ThinManager Servers defined in the ThinManager Server Wizard will be listed in the Source and Destination columns. Highlight the desired source ThinManager Server in the Configuration Source column and the ThinManager Server you wish to copy the files to in the Configuration Destination column and select Next to continue to the next step.

Synchronization Differences

The ThinManager Synchronization Wizard will list the files being updated, including the firmware, termcap database, modules, and the configuration. Select Next to continue.

ThinManager Server Synchronization Confirmation

The ThinManager Server Configuration Wizard will show the selection of ThinManager Servers that were chosen to be acted upon before prompting for a conformation of the synchronization before proceeding. Select Finish to finalize the changes.

Note: The Synchronization program does not compare and contrast, then make changes back and forth. Synchronization will take the files and configuration from the source ThinManager Server and overwrite the corresponding files on the destination ThinManager Server.

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IP Configuration of Terminals

Each ThinManager Ready thin client needs to be configured to boot from both ThinManager Servers when using redundant ThinManager Servers. This differs when using DHCP or a Static IP Address. See DHCP or Adding Units with BootROM 5.01 for details.

Thin Clients Using DHCP

ThinManager Ready Thin clients are set by default to use DHCP to receive an IP address. The thin client also receives the IP address for the ThinManager Server. This is done by configuring Option 066 in the DHCP Server Program.

DHCP Server Options

Open the DHCP Server program by selecting Start>Settings>Control Panel>Administrative Tools>DHCP on a Windows 2000 Server and Start>Administrative Tools>DHCP on a Windows 2003 Server. Highlight the scope and select Action>Options. This will launch the Server Options window.

Scroll to Option 066 - Boot Server Host Name and add the IP address of the the redundant ThinManager Servers in the Data Entry field, separated by a space. This will pass the IP addresses of the ThinManager Servers to the thin client, enabling it to boot from either.

The thin client will try the first, or primary ThinManager Server. If it can't connect to it, it will time-out and try the second ThinManager Server listed.

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Thin Clients Using Static IP

The Static method uses IP addresses that are entered on the unit instead of being assigned by a DHCP server. Set the static IP address by booting the thin client and interrupting the boot process by pressing the spacebar when prompted.

Press Any Key to Configure Message

The thin client will display a IP Configuration Menu.

Default IP Configuration Menu

Select the A key and type the IP address for the thin client and press the Enter key..

IP Configuration Menu

Once the client has an IP address entered, the other menu items are available.

(A) Terminal IP Address - This should be a unique address for the terminal.

(B) Primary ThinManager Server IP Address - This should be the unique address for your main ThinManager Server.

(C) Secondary ThinManager Server IP Address - The Secondary ThinManager field allows the terminal to use two ThinManager Servers. If the terminal cannot connect to the Primary ThinManager Server, it will connect to the Secondary ThinManager Server to receive its configuration. If you are not using a Secondary ThinManager Server, set the IP address to 0.0.0.0. ·

Enter the IP address of the Primary ThinManager Server after typing B and enter the IP address of the Secondary ThinManager Server after typing C. Type S to save when finished.

The thin client will try the Primary ThinManager Server when it boots. If it can't connect to it, it will time-out and try the Secondary ThinManager Server.

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(Updated 7/19/2007)