"We recently replaced eight standalone, rack-mount servers that were five years old, and due for replacement with two rack-mount host servers designed to run the equivalent of the existing system as virtual machines (VMs). There are currently eight virtual machines running on each host server in the new configuration. VMWare ESXi 5.0 is the virtualization software, and Wonderware Archestra is the HMI/SCADA system.
"The following standalone machines were converted to VMs, and are each running fully redundant with the ability to have one host machine fail with no loss of SCADA functionality:
- Archestra System Platform Object Servers
- Wonderware Historian
- Domain controller
- Terminal server
- I/O servers (communications to PLCs)
"This is our first use of virtualization in a production environment, and there were no real issues encountered in the development of the virtual system. Wonderware's testing and support of their system in a virtual environment provided a solid basis for conversion, and performance is very satisfactory to date. The system has been in operation for about four months.
"As we see it, benefits of virtualization include the ability to add virtual machines to host servers to add/expand SCADA system capacity. After the existing system was virtualized, additional SCADA expansion required more Archestra System Platform Object Server capacity. The host servers were initially purchased with four CPU sockets with only two used, and with only half of the memory sockets used.
"Two additional CPUs and additional RAM were added to the host, and the SCADA system capacity was increased. There was no SCADA system downtime required since one host server hardware upgrade was performed at a time, each in a matter of hours.
"Additional VMs are being added to the hosts to provide the SCADA system Archestra System Platform Object Server capacity. Engineers continued to develop and configure the new production VMs on temporary computers, while the production hardware was upgraded. Development was not interrupted once the need for additional hardware capacity was identified.
"Virtual servers have been used in our development environment for about four years with VMWare Workstation. The development VMs run on tower servers or workstations. The VMs run development software for HMI, PLC, Historian, Reports and other applications.
"The benefits of the development environment virtualization include reduced maintenance and downtime for the development stations because new versions and patches can be applied to copies of the original VM. Old versions of programs are not lost, and new hardware is not required to keep multiple versions of programming software.
"New versions can be installed on a new VM or on a copy of the existing VM. New features of PLCs and programming software can be used more easily since additional development workstation hardware is not needed to create the new development environment.
"We are using thin client visualization in water and wastewater treatment plant environments. A recently completed project provided eight operator workstations around the plant using thin clients rather than thick client PCs as in the past. The initial benefits were greatly reduced initial cost of workstations and HMI licensing.
"On-going benefits include reduced maintenance of hardware and software on the thin clients. Thick client PCs are usually replaced every three years, but the expectation for thin clients is that they will last up to 10 years, and the thin client software technology can be supported on the hardware platform through that time period."
