I have an question regarding transparent server redundancy. I´ve read in another thread:
My questions are:OPC UA defines two main modes for server redundancy, non-transparent and transparent. Non-transparent has the sub modes Cold, Warm and Hot.
In the non-transparent case, all servers in the redundant set have their own Server URI and Endpoint URLs. Every server in the redundant set provides a list of the other redundant servers in the set (Server URI) and the sub mode (Cold, Warm or Hot). With this feature a client need to know only one server and can find the other available servers through the information in the server object (Objects -> Server -> ServerRedundancy). The advantage of non-transparent redundancy is that it is easy to support on the server side. The disadvantage is that the client needs to do something to benefit from redundancy. But it would be easy to implement a generic support in the client with the information provided by the server.
In the transparent case, all servers in the redundant set have the same Server URI and Endpoint URLs. The servers are running in a cluster with the same IP-Address. A client cannot connect to a specific server but he can request the list of available server and their status in Objects -> Server -> ServerRedundancy. The advantage of transparent redundancy is that the client needs to know nothing about redundancy to benefit for the redundant servers. The disadvantage is the higher effort on the server side.
The C++ Server SDK from Unified Automation supports both main modes for server redundancy, non-transparent and transparent. For transparent redundancy an additional module is needed that is not part of the standard SDK. It is available on request. The non-transparent configuration can also be used in the UaGateway V1.2.
Does the OPC servers have to have the same endpoint addresses?
If the transparent redundancy is used, is there a posibility to let know the client about that the redundancy handover occured?
The thing is: we have 2 identical controlling devices connected to the network with different IPs, and each device has an OPC server. Devices acts as redundant. (both can handover the controlling) We want to implement transparent redundancy, but the IPs has to remain the same and furthermore if the handover occur we have to warn the operator that the second device is out of order ...
Thank you for your answer...