Virtualisation is the separation of an IT resource from specific physical hardware. This property is usually managed by a specialised software layer called a hypervisor, which provides another abstraction layer beyond that used by computer operating systems. Virtualisation can be applied to any IT resource including servers, storage, desktops and networks. For example, server virtualisation enables multiple virtual servers (called ‘guests’ in virtualisation parlance) to run on one physical server (referred to as a ‘host’). This reconfiguration is often called ‘server consolidation’, since a given set of applications are executed on a reduced number of physical machines. Virtualisation can provide business and technology benefits such as greater IT resource utilisation, better security and easier system administration.
In IT, virtualisation has become a highly mature technology. Virtualisation is a foundational layer of all cloud computing architectures, which operate exclusively on virtualised resources. In today’s market for process automation systems, many suppliers offer products and solutions that employ virtualisation. Virtualisation also plays an increasingly important role in ARC Advisory Group’s evolving Collaborative Process Automation System (CPAS) vision.
Virtualisation vs. simulation vs. emulation
In the context of virtualisation, the hypervisor presents resources to guest operating systems as if they were physical resources. A guest operating system cannot ‘know’ or determine whether it is running in a physical or virtualised environment, so it behaves exactly the same way in either one.
In software simulation, matching actual system behaviour is important, but simulation software is usually instrumented with specific features suited to its use. For simulations used in software development this may include visualisations of code and data states, timing, etc. In operator training simulation, special software features for simulator time stoppage, time scaling, and rapid return to specified initial conditions do not correspond to target system capabilities.
Emulation usually refers to application software that provides a pseudo-environment for executing other software. Most often, this involves support for non-native hardware instruction sets and processor architectures. Such software can be designed for operational use or for software development. The most popular emulation software applications emulate a Microsoft Windows OS on either Apple or Linux OSs.
Virtualisation benefits in CPAS
Since virtualisation today can only be applied to some parts of process automation systems, it can be difficult to assign specific economic value to the technology. Virtualisation plays an important role wherever server hardware is used in the automation system. This is at levels two to four of the ISA-95 manufacturing model. Today’s automation suppliers offer system configurations that feature server consolidation. Multiple HMI machines and other application servers are replaced by virtual machines. A small number (usually one or two) of more powerful hosts support these virtual machines. Besides being more powerful, the new servers incorporate levels of redundancy with respect to power, storage, compute and network resources.
Server consolidation benefits include removal of physical equipment and freeing rack or panel space in congested control areas. Power requirements and system administration burden are also reduced (though the remaining administration work is technically more complex).
The largest benefit to end users of server consolidation in process automation systems is the decoupling of the automation software from specific configurations of PC or server hardware. For years, many HMI and other automation system functions have been implemented on PC hardware. Plant owner-operators and automation suppliers have struggled to support these systems due to the short lifecycle of PC products. By virtualising such a system, it can be more easily supported once replacement hardware is no longer available. This higher degree of hardware independence helps extend automation system life and reduces production interruptions due to automation system upgrades.
At lower levels (1-2) in the ISA-95 model, automation functions are implemented in embedded systems (e.g., process controllers, process I/O equipment, or field devices) that are managed by a real-time OS. While these devices can be simulated or emulated, strictly speaking they cannot be virtualised as is. Instead, their embedded software must be modified and/or ported to some degree to operate in a virtual machine environment. Most automation suppliers have developed products that now provide this functionality.
For the field devices and actuators at level 1 of the ISA-95 model, there is not much to report at present about virtualisation. Simulation software/hardware is available for some field networks. Several technologies are becoming available (EDDL, FDT, FDI) for managing field device parameterisation, configuration, and diagnostics. However, the commissioning of field devices remains largely a field activity and has not yet benefitted from virtualisation or simulation to the same degree as other areas of process automation systems.
Virtualisation benefits for the plant asset lifecycle
For process manufacturers, virtualisation technology can bring significant value to their installed base of automation systems as well as to automation projects for new plants. For installed systems, the benefits come from replacing dedicated servers with virtual ones. In new installations, the benefits come from schedule compression resulting from the ability to develop the system configurations and applications in a virtualised environment. End users should evaluate specific benefits that accrue both during the design and build phase and the O&M phase of the plant asset lifecycle.
Benefits during the design and build phase centre around two major areas. First is the reduced space and utility requirements of an automation system incorporating server virtualisation. These reductions can be dramatic and result in substantial savings in high-cost installation areas, such as offshore platforms. Note that to take advantage of such savings, these reduced requirements must be known during the early FEED stages of project engineering so that the project civil and mechanical engineering designs take advantage of the reduced system power and space requirements. Without a main automation contractor (MAC) structure, projects are not likely to realise these benefits.
Second is the ability to engineer the automation system without access to the target hardware. This leads to any number of changes in the configuration and engineering process, as automation supplier and project engineering teams work using a virtualised automation system for almost all their project engineering activities. These changes can include:
* Employing a geographically distributed project team working from different locations on the same virtualised automation system.
* Reduced project dependencies between system hardware deliveries and system configuration and engineering deliverables.
* Conducting a ‘VFAT’, a factory acceptance test for the automation system using a virtualised system.
* Late binding of the system software and configuration with the target hardware.
* Concurrent development of operator training simulators and automation system engineering.
Virtualisation benefits during the O&M lifecycle phase can also be significant. Reduced requirements for physical space and electric power can be valuable in space-constrained brownfield sites. The de-coupling of updates to system hardware and software is another important benefit. Simplified HMI and other server hardware may result in MTTR reductions. Virtualisation should also enable end users to maintain development/test systems and OTS installations with less effort; though ARC believes the case for these benefits is not yet field proven. Finally, system administration, backup and disaster recovery processes can be simplified and less disruptive, though they will be more complex technically.
For more information contact Paul Miller, ARC Advisory Group, +1 781 471 1126, [email protected], www.arcweb.com
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