Inquiry: Dual Logging with OPC UA
Hello,
Is it possible to set up the OPC UA collectors to collect data on the same OPC server at a time? Then on the event that the main OPC server is "down" the OPC collectors will shift collecting data to the back up OPC server.
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Morning Kevin. Let's work backwards from the database first. The Receiver can receive two identical streams for the same tag. The historian follows a 'first-in-wins' methodology. When it receives identical timestamps for the same tag, it writes the first value and ignores the second, regardless of any quality score differences.
If you changed your architecture and rather than 'shifting' from one OPC server to the other, but instead just had simultaneous streams running constantly, the Canary Historian would have no duplication issues. You would just use the exact same logging configuration on each OPC Collector, pointing to the exact same DataSets.
We do not have any configuration that would allow for a 'switching' between two different OPC servers should one not be available.
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Hi Jeff Knepper, great to know that. Is this the only / recommended approach in high availability scenarios (where there are redundant OPC UA servers)? Seems like having a way to hot-swap the source OPC UA server in case of failures instead of running simultaneous streams to OPC Collector would save a lot of network bandwidth.
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krish I think we would be able to cancel any unnecessary bandwidth by following a best practice. Canary's OPC Collector and Sender should be installed local to the OPC server. The Sender communicates across the network to the Receiver and Historian. Sender also provides store and forward with data buffering should historian not be available due to network or server issues.
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Jeff Knepper Correct me if I am wrong. The recommended approach is still not going to avoid sending two identical streams through the network for the same tag. I think a more elegant approach is to allow hot-swapping of the source.
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krish To help clarify my understanding.... you have two OPC Servers, one primary (A), one cold standby (B). Am I correct in stating that B is only employed when A is lost or not operable?
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