Virtualisation of automation systems – a brave new worldAuthor Vladimir Pöyhönen
Automation has developed at a rapid pace in recent times. The surge in development has seen automation suppliers and component manufacturers for process control launch new generations of process controllers and bus and I/O components on the market. The use of ICT technology and databases has increased in distributed control system (DCS). This increasing use dictates that we to come up with new ways of efficiently utilising the computational power and opportunities computers present. ICT virtualisation can achieve significant savings in the delivery of automation systems and in producing high levels of system flexibility and usability.
Virtualisation refers to the use of virtual computers in one or more servers, the physical resources of which are jointly used by the virtual computers with the use of virtualisation software (Hypervisor). A virtual machine is a program-based object which corresponds to a physical computer in terms of logic and functionality.
Usually the end user uses a virtual machine via a terminal which is connected through a remote connection, such as Remote Desktop Protocol (RDP). Virtualisation technology has rapidly become popular in the IT office environment and is currently finding a home in ITC process automation.
Development work and tests conducted at Elomatic on the use of virtualisation technology in automation systems indicate that ICT virtualisation is indeed possible and the results are very promising.
The development team’s vision of an implementation strategy for automation systems is depicted in Figure 2. It shows the most essential parts of the DCS implementation with the use of virtualisation. The device implementation differs from that shown in Figure 1 because the usability requirements differ between the Demilitarized Zone (DMZ) and Process Control Network (PCN). This has an impact on duplication, which means that a single blade server can be used in the DMZ. In the PCN, a cluster needs to be built of separate servers and Network Added Storage (NAS) drives located in different places. The DCS servers of a large ship’s control system and other critical IT components are, for example, located in different parts of the ship.
More licences but less hardware
A basic cost analysis has shown that in virtualised systems the share of licences increases and that of hardware decreases. The reason is that the management of a virtualisation solution requires a new software platform and software licences. A redundant NAS implementation, for example, requires not only special hardware, but also software for a high availability (HA) network drive. See Figure 3.
In virtualised systems several computers and servers are replaced by a few more powerful servers and operator terminals, so that the quantity equals the number of desktop computers. In addition to software and hardware changes, the system changes in terms of management, maintenance, usability and its expandability. For example, the migration of a virtual machine is only possible in a virtual environment, and the use of migration in maintenance improves flexibility and efficiency. In other words, the diversity of the new system structure improves efficiency and user-friendliness.
Total cost ownership (TCO)
The total cost of ownership for the automation life cycle plays an important role when analysing the use of virtualisation technology. The initial costs may be higher, but no further hardware and software upgrades are required for the automation system, which means that the TCO is significantly lower than that of a traditional implementation.
Figure 1. A common distributed control system (DCS) implementation
This factor cannot be ignored, and as a result, large automation suppliers have, in recent years started to offer partly-virtualised solutions. Honeywell stands out from other suppliers as it also offers HA solutions for virtualisation. This technology guarantees flexible and cost-effective automation deliveries.
Automation companies need to keep up with the changing world. Virtualisation expertise and specialisation delivers far superior benefits compared with traditional approaches. It provides companies that embrace these technologies with a clear advantage as they are able to serve their customers in an entirely new way, for example, in automation system procurement and implementation. Learning new concepts as well as developing and applying what was learnt are vital skills in the modern world.
Figure 2. DCS implementation concept with use of virtualisation
Figure 3. StarWind iSCSI NAS implementation
The original text was published in our 1/2014 Top Engineer magazine
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