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Thread: Redundant Servers - SQL Evacuation

  1. #1
    adrian.mcgranaghan Gast

    Default Redundant Servers - SQL Evacuation


    we currently have a setup that consists of two PCs acting as servers, one is the primary and the other is the standby. We are receiving some values from an I/O device over the IEC-60870-5-104 protocol. We are then archiving these values before evacuating them to an SQL database.

    We have configured each server to evacuate to it's own SQL database. Data from the primary server is evacuated fine but data from the standby server never seems to be evacuated.

    Even when we take the primary server offline and stop runtime, the standby server (which becomes the primary server now) still does not evacuate to the SQL database.

    The settings in the historian archives are the same for both the primary and standby server, the only difference being the actual SQL database that they are evacuated to.

    Can anybody point me in the right direction as to what could be the problem?

  2. #2
    adrian.mcgranaghan Gast

    Default Re: Redundant Servers - SQL Evacuation

    Update: It seems that when I deactivate the network property on the standby server (uncheck the 'Network Active' box) then it seems to evacuate to its SQL server.

    I kept the network active property checked on the Primary server, unchecked it on the standby server and both servers are able to write to their own SQL databases. The synchronisation between servers also seems to be working.

    Is this functionality correct?

  3. #3
    louis.paglaiccetti Gast

    Default Re: Redundant Servers - SQL Evacuation

    Hi Adrian,

    Let me say first, the use of a SQL Server for zenon Historian is completely optional. zenon offers its own native, high-performance file format for historian data without the need of a SQL Server.

    The first major issue you have right now is you have a network project with server & standby. So when both servers are online and a project change is put onto the standby server, it is overwritten by the project configuration of the running primary server. This is intended and for the purpose to keep the servers synchronized, along with the clients. For the zenon network and redundancy to function as intended, you want the same project and configuration active on both primary & standby servers.

    If your requirements are to store historian data on a SQL server, then you can of course use the zenon SQL Evacuation.
    On a redundant system (server & standby), the each historian archive can be configured to evacuate to a single SQL Server.

    Many customers run the SQL server on its own separate dedicated PC, mostly for availability reasons. This is my recommendation as well.

    In this architecture, both zenon servers evacuate historian archives to the same SQL server. If the primary zenon server fails, the standby zenon server will automatically take over the role of a primary, and begin evacuating (as well as reading e.g. via trends) from the SQL Server. If perhaps the centralized SQL server is offline or otherwise unreachable, the zenon runtime will locally cache the historian data until a point where the connection to the SQL Server is valid again. Then, the archive will be flushed automatically to SQL.

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