Introducing high availability and load balancing for central print servers
Critical business processes often still rely on printing. With Windows Server 2012, Microsoft no longer supports print clusters. This leaves printing without a safeguard. The High Availability Mapping function gives you the opportunity to both establish fail-safe reliability for your ThinPrint Servers, and to evenly distribute the load between them.
To do so, you set up, using AutoConnect on your remote desktops (terminal servers or virtual desktops) or using group policies, groups of print servers to be managed. For each group, you need to determine whether it will have high availability (i. e. reliability) or load balancing applied to it.
Note! Since ThinPrint version 11.0, load balancing or failover using the Registry value DPMTries isn’t supported anymore.
When ThinPrint is installed on a remote desktop (terminal server or virtual desktop), three new Start menu items are added:
- ThinPrint Configuration
= ThinPrint configuration in the Microsoft Management Console (MMC), see below
- ThinPrint Self Service
= printers are selected by the user(s), see ThinPrint Self Service
= classic Printers folder for a better overview (when MMC-based Print Management is not available)
- Open the ThinPrint configuration console (see ThinPrint Configuration in Illus. above).
- Select the High Availability Mapping option there.
- Firstly, you need to determine which print servers are to be managed together. Select Create Group for this. That will open the window shown in the next Illustration.
- Enter a name for the group, and select the type:
- either Failover
(for reliability i.e. high availability)
- or Load Balancing
(to evenly distribute the printer connections on the servers for this group)
- either Failover
- Then use the button (see arrow) to consecutively add the print servers on which a ThinPrint Engine is installed to the Active Directory. Confirm each window with OK.
With the print server groups, rules no longer need to be defined in the AutoConnect tables for each printer per print server, but only per group. Thus AutoConnect connects either – in Failover mode – the printers from the print server with the highest priority or – in Load Balancing mode – connects the printers from the specified print servers alternately.
AutoConnect – installed on remote desktops (terminal servers or virtual desktops) – exchanges information with the ThinPrint servers via Remote Procedure Calls (RPCs). A print server here can have any of the following statuses:
Provided there is an RPC connection, the status of the print server on both machines (remote desktop and print server) is identical (immediate replacement in case of a change). However, if an RPC connection has not been established, the attempt to connect will be repeated regularly. If an RPC connection can’t be made or
an existing connection is disconnected (and the remote desktop detects this), the print server switches to the status Failed.
A print server’s status is not dependent on the RPC connection alone:
- A print server with the status OK, which then experiences an error while connecting printers (for example, Error 1722 – if the spooler of the print server is not running) switches firstly to the status Suspicious and, after the maximum number of failed attempts has achieved, to the status Failed.
- A functioning print server can be manually set to the status Maintenance.
If a print server drops out, it switches over to the status Failed. Then AutoConnect deletes all the printer connections that existed with this print server in all user sessions. It then connects the same printers to the print server with the second highest priority (auto-remapping). If the functionality of the failed print server is restored, then it is automatically brought back into operation. Until all the printers are reconnected to the first print server, both print servers remain active.
- The same batch of printers are set up on each of two ThinPrint Servers – cps47 and cps50.
- On the remote desktop or in group policies, both print servers are set as the Failover type in the group “HA”. Both print servers have the status OK.
- Furthermore, on the remote desktop or in group policies, an entry has been made in the AutoConnect table Map Additional Printers, to connect the printers from this group in the sessions.
- The two printers
• Lexmark T650#tphubc25e75:1
• HP Color LaserJet CP3505dn#tphubc25e75:2
were connected in the session by the print server with the higher priority – in this case, cps50.
- The print server with the highest priority drops out – here cps50.
- As anticipated, the same printers are, shortly after, connected by the second print server – here cps47.
See also next screenshot.
|Edit Group||change the settings for a print server group, e. g. change the type from Failover to Load Balancing|
|Duplicate Group||create a second group with the same members – e. g. to create additional groups faster or to use the same server simultaneously for reliability and for load balancing|
|Remove Group||delete this print server group|
|Change server status to→ OK||restore the server concerned – from the Maintenance mode or from the Suspicious status – to the OK status (= ready mode)|
|Change server status to→ Maintenance||place the print server concerned into Maintenance mode|
|Refresh||retrieve the current information from one or all print servers of a group|
See also next screenshot.
|Automatically remap printers||If a print server changes status to either
Failed or Maintenance, the printers that were connected with that print server are deleted automatically and connected with another print server.
|Threshold for assigning failed status||Failures when attempting to connect a printer to a print server are counted. After the number of failed attempts specified here, this print server is set to status Failed.|
|Cancel connection attempt after (s)||If there is no response from a connection attempt after the time defined here, the attempt is aborted and the print server immediately set to status Failed (timeout in seconds).|