Redundancy

[minhnt152]

Hi,

We have project that need HA redundancy.
Can you develop this function?
We can pay for the development.

Thanks

[manjey73]

Use RapidGate it seems to be designed for this purpose. Or are you interested in hot swapping on the fly ?

[Mikhail]

Hi,

Please provide detailed requirements for redundancy that you need.

[minhnt152]

Hi,

We have a system for gasoline depot that manage the gasoline tank and tank fill terminal which has some batch controllers.
There are two servers that works as H-A, they will manage the scada system, call Primary and Secondary servers. At one moment, only one server will communicate with the devices and it will synchronize with the remain server. If the main server (A) go down, the second server (B) will detect and step up to be main server with full function. After A is recover, the (B) still work as main and synchronize data to A.
The server also need to get the order from SQL, to control down to the scada.

Thanks

[Mikhail]

Hi,

Currently there are the following options:
1. Manually start and stop Communicator services on the servers.
Data transfer can be performed by Rapid Gate module.

2. Use 2 servers in parallel. Both of them poll the devices. To do that, you need a hardware gate that allows multiple connections. Like Modbus TCP gates.

In the future, switching logic may be implemented by Auto Control Module be sending start/stop communication lines commands.

[manjey73]

You can synchronize the time to achieve parallel polling by two Scada systems, by separating the polling time. I have already tested this on RS485 lines, it works. There may be collisions when restarting the server since the initial poll is performed immediately

[minhnt152]

Hi Mikhail,

I want it to work automatically, not by manual.
And if we use the communication work in parallel, it will make high data rate on the gateway, which i don’t want.

The standby server does not duplicate the primary server’s functions. In that scenario, both servers would have to communicate with the PLCs, thus doubling the load on the PLC network and reducing system performance. A better alternative for a client/server system is one in which only the primary server communicates with the PLCs. The primary server also communicates with the standby server, continually updating the plant’s status. If communication is interrupted, the standby server assumes the primary server has failed and takes over the role as the primary server. When the primary server is repaired and returned to service, it reads the plant’s status from the standby server and resumes its role as the primary server. Data is automatically backfilled and the two servers become synchronised again as the standby server reverts to its former role.

Thanks

[Mikhail]

Hi,

What is the source of the text “The standby server does not duplicate the primary server’s functions…” ?

To implement the described mode, there should be a separate supervisor service that switches servers. We can develop it if needed by a custom contract.

[minhnt152]

Hi Mikhail,

The source article is: https://www.machinebuilding.net/why-and-where-to-use-redundant-scada-systems

We need the system to not stop if there is a problem with a server. When one server down, the remain server must continue the work smoothly.

For example, while filling the tank for gasoliine truck, the process can’t stop.

Thanks

[manjey73]

To fill the tanker, you must have reserved PLCs and I / O modules for critical tasks. This is not a Scada function. Think about security first. It is not necessary to burden the software with something that does not belong in it. I apologize for my English, I use an online translator

[minhnt152]

Hi Manjey,

The fill tank is a group of batch process.
We need the scada to collect the order, then check the truck, then verify the station, then fill tank, then re-check tank… And the process will have to continue even if the primary scada server is fail. It can’t be restart from begining. That why we need a redundant server solution.
The PLC also designed to have redundant CPU already.

Thanks

[Mikhail]

Hi,

I agree with the point of view that a process should not depend on computer in any case. All critical tasks should be managed by PLCs.

Talking about SCADA redundancy, a custom development is needed to implement it as described. Otherwise, use 2 parallel independent communication lines.

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