The NetMan Desktop Manager replication mechanism helps ensure high availability of your NetMan Desktop Manager system by providing for failover backup. The installation of a replica set gives you excellent protection if the primary NetMan Desktop Manager server ever fails.
Basis
The replication mechanism is based on the NetMan Desktop Manager database, which supports asynchronous replication of the data between database servers. Data is written by only one database server: the primary database server. All database servers are incorporated into one replica set. A replica set is made up of at least three servers: one primary and two secondary database servers. Additional secondary database servers can be added, as long as the total number of database servers (primary plus secondary database servers) is an odd number (3, 5, 7, etc.). A system with three servers can cope with the loss of one server; if there are 5 servers total, the loss of two can be absorbed, and so forth. The primary installation of NetMan Desktop Manager is on the primary database server. On both of the secondary database servers, a secondary NetMan Desktop Manager system is installed.
Operating principle
Availability of the NetMan Database is essential for NetMan system availability. The decisive factor in determining availability is the NetMan Service. If the NetMan Service on the primary database server cannot be accessed, then the database on that server cannot be accessed either, and server failure is reported. This triggers the failover mechanisms. The secondary servers elect a new primary database server, which takes over the tasks of the failed server.
Note: Replication of NetMan data affects only the contents the NetMan Database! For complete failover capability, the replacement primary server must be able to access all the same resources to which the failed server had access. The NetMan Replication feature affects only NetMan system components – no third-party software is covered. To put replication into effect, your NetMan server should ideally be systematically disconnected from your Remote Desktop Session Host. Unavailability of the applications published through your Session Host is not taken into account by the NetMan replication mechanism. All data that is required for proper functioning of your Scripts should be stored in your NetMan Database.
NetMan Desktop Manager updates: It is essential to keep in mind that when updating your NetMan Desktop Manager system software, all secondary servers should be updated first, before you update the primary server.
The chapter entitled "Install the Replication System" outlines the procedures for replica installation and configuration.