Feature Communications & networking Server virtualisation is now a reality


While the benefits of server virtualisation at the corporate data centre are receiving a lot of attention, it is also now beginning to appeal to manufacturers. Virtualisation can, however, bring both advantages and challenges. Rockwell Automation provides six tips on how to optimise server virtualisation


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erver virtualisation is the practice of using a software layer to let one physical computing server run multiple virtual machines. It helps manufacturers cut costs by consolidat- ing a number of applications on the same physical server.


Implementing virtualisation in the manufacturing environment began with applications deemed less critical, but it has now moved into the business- and mission-critical realm. Manufacturing Execution Systems (MESs) and related automation applications can gain advantages from virtualisation. However, the risk and cost of service interruptions become higher as manu- facturing applications become more powerful. Establishing and using best practices can help you get the most from virtualisation without compro- mising your operation’s availability and performance. Here are six tips to help: 1. Know Your Application Begin by characterising your software application and its workload. Which resources does your application con- sume? How much? When? How much headroom do you need for peak times and temporary surges in demand? Performance degradation may mean the application could become unavailable and provide poor response time. Also make sure you conduct an appropriate risk assessment - not every application is a good candidate for vir-


ata Steel is trialling a thermocouple from ABB that generates the energy needed to drive it from the heat in the surround- ing process. Combining this energy harvesting technology with wireless communications effectively eliminates the need to run any wires to or from the device. “It would be a dream come true for an engineer to have a self-powered wireless thermocouple,” said Nikhil Kumar, area electrical engineer for blast furnace No.5 at the Port Talbot steelworks. “You don’t have to run any cable, which saves money on the installation and also eliminates the risk of burning or damaging the cable during operation.” The ABB device hasn’t missed a single reading in the three months since it was installed, and has not had to resort once to its on-board battery backup, according to Tata Steel.


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During a trial, the thermocouple was installed on one of the plant’s steam lines, which operates at 120˚C. The harvesting technology requires a temperature difference of just 30˚C between the process and its surroundings in order to drive the instrument’s electronics and transmit its readings. This contrasts with the results from a second thermocouple, which was installed nearby to test what happens when an energy harvesting instrument is installed without the necessary temperature difference. This instrument has had to rely on its battery for the entire duration of the test. Tata Steel has also been trialling wireless adapters fitted to a pair of pressure transmitters. The adapters enable all the instruments to communicate with one another, and with the plant’s control system via a wireless gateway. Kumar says the instruments are able to talk to the gateway up to 50m away if there is a clear line of sight. In practice, numerous obstruction bring this down to a respectable 20m from the gateway. “It hasn’t dropped a reading during the entire trial,” said Kumar. ABB Measurement Products


www.abb.co.uk 18 Enter 228


tualisation. Typical examples are I/O- heavy applications and performance- sensitive environments that are not easily characterised. 2. Understand Tradeoffs


Because virtual servers are easy to set up and don’t require the same manage- ment approval as hardware purchases, some companies are experiencing “vir- tual server sprawl.”


Expect some performance penalty as well; how much depends on your application and the virtualisation tech- nology you use. Maximising applica- tion availability and performance on a virtual machine requires some skill. Also check how virtualisation will affect your software license fees. 3. Seek Enterprise-Strength


Technology


Remember that the virtualisation layer has the potential to be a single point of failure for all of the virtual machines it supports. Remember, soft- ware reliability increases as the amount of code and its complexity decrease. Look for virtualisation software that is small, compact and controlled – like an appliance. Virtualisation and avail- ability solutions that are simple to con- figure and maintain help reduce costs and your exposure to downtime due to operational errors.


4. Plan for Business Continuity Reliable availability and perfor- mance become more important the


Eliminating cables makes dreams come true Virtual Machine 1 Virtual Machine 2 Virtual Machine 3 SCADA


Legacy App


Oracle DB


OS OS OS Virtualization Layer Single x86 Server


As server virtuali- sation technology matures, it’s


becoming suitable for the much more exacting demands of mission-critical manufacturing applications. You can gain new capa- bilities and reduce costs if you choose appropriate tech- nology and plan properly


more that you depend on an IT resource, and the more that resource is integrated with other systems. To miti- gate the risk of plant operations being interrupted, institute backup and disas- ter recovery measures for the physical servers that run your virtual machines. 5. Simplify with Robust Hardware Virtualisation reduces physical com-


plexity, but adds equally real complex- ity in a virtual dimension. Without proper planning, this can be a problem because IT skills are in short supply at the average manufacturing facility. Clustering multiple servers is one way to achieve high availability. But, implementing virtualisation on a server cluster adds another layer to deploying and administering a cluster. For exam- ple, a server must be running to migrate its workload to another member of the cluster. Therefore, when a double-bit memory fault causes a server to crash, its workload can’t be transferred, data will probably be lost and a reboot will be necessary.


Check with server hardware or virtu- alisation software vendors on which hardware faults can be predicted enough in advance to support a live migration — what percentage of the hardware is covered? In the case of a full restart, what is the worst-case fault detection and restart time? Is the man- agement software making fail-over decisions robust, or for that matter, run- ning on a robust platform? 6. Don’t Let I/O Sink the Ship Incompatibilities related to I/O inter- faces can cause system instability and performance problems. Establish that I/O devices and drivers are compatible with the virtualisation technology you plan to use, and be ready to resolve incompatibility problems.


Rockwell Automation T: 0870 242 5004


Enter 229 E: ukmarketing@ra.rockwell.com JULY/AUGUST 2013 Process & Control


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