Synchronized redundancy

Redundancy is an important feature in any system to increase system availability, but in the critical environment of a custody transfer metering system with round-the-clock operation it is an essential function.

eXLerate offers fully synchronized redundancy, which operates on a Duty/Standby principle in a Client/Server architecture. Redundancy is fully implemented in our product, so you do not have to waste your time while engineering your application.

Redundancy is available at various levels, including device level, server level, and individual I/O level. Many objects/entities are synchronized in a redundant client/server architecture, as illustrated below:

Synchronized servers

In a redundant system, one of the servers is designated as the Duty Server, while the other servers act as Standby Servers. Each Standby Server and each Client in this context are fully synchronized with the Duty Server, including:

• I/O from & to hardware devices
  Signals from field devices may be obtained from various servers, and shared with standby servers and client computers.
  
  
• Parameters and settings at a device or HMI
  When the operator enters a value, such as an alarm limit or PLC setting, at either client or server computer in the system, all computers and pertaining field devices are automatically updated.
  
  
• Alarm summary and history
  The alarm summary in all computers is obtained from the duty server. Operator commands, such as alarm acknowledgements, are automatically processed by the duty server.
  
  
• Reports & historical trends
  Reports & historical trends are generated by the Duty server, and are synchronized from the duty server to standby servers. Client computers only retrieve reports and trend data from the duty server computer.
  
  
• Operator commands & control logic
  Operator commands as well as application control logic are synchronized between connected computers by the product software.
  
  
• MySQL database tables
  Comprehensive support for relational databases includes full synchronization. Data stored by the Duty server is automatically synchro­nized and distributed to all Standby servers.

Switchovers on failure

On failure of the Duty Server, there is an automatic switchover from Duty Server to a Standby Server, and vice versa.

When the Duty Server has a failing connection with a particular hardware device, it is able to retrieve the pertaining data from a mirroring Standby Server without effective loss of data.

This redirection of all I/O is fully transparent, automatically available and is fully managed by the product software. This is another unique and powerful feature, effectively making redundant hardware links obso­lete. 

Transparency in data

All computers have exact identical application software. Data is transparent between clients and servers in regard to real-time data, parameters, alarms, trend data, reports and system events.

In-use data is consistent in all connected computers, either Client computer, Duty Server computer, or Standby Server computer.

Our advanced distributed synchronization technique allows for full redundancy at server computer level, and yet processes all involved data as if existing in a single monolithic system.

This functionality supports the highest degree of system integrity, consistence of configuration and application data and bump less switchovers.