Data Centre virtualisation and its demands on UPS technology

Continued growth in data centre virtualisation is inevitable, given the advantages it offers. However, the strategy creates significant challenges for data centre infrastructures. In this article Alan Luscombe, Director at KOHLER Uninterruptible Power Ltd., a KOHLER company, describes how modern, modular UPS technology can assist data centre operations managers and owners in meeting these challenges.

Data centre virtualisation is a powerful strategy that continues to enjoy steady growth within data centre operations. Its strength comes from making the IT process more productive and agile, delivering higher levels of service at lower prices. In fact, market research analysts Reportsnreports predicts a CAGR growth in the global storage data centre virtualisation market of more than 24% from 2015 to 2019, while according to Arbor Networks, AT&T expects to virtualise and control more than 75% of its network using a software-driven architecture by 2020.

Data centre virtualisation and its power challenge

Along with its proven benefits, virtualisation also has significant implications for data centre infrastructures, including uninterruptible power supplies and other key components. Data centre virtualisation consolidates multiple IT resources onto a single server, initially reducing the number of servers and power required. However, over time, increasing business demand typically draws the freed-up servers back into operation, with utilisation heavier than ever due to virtualisation. VMW claims that data centre virtualisation can increase hardware utilisation from as low as 5% to as much as 80% – and all this drives power demand significantly higher than original levels.

Accordingly, UPS power supplies have to be flexible and scalable to cope with this dynamic and growing load demand. As initial data centre virtualisation decreases the load, it should be easy to take some UPS capacity offline to avoid unnecessary UPS systems powering and cooling. Adding capacity to facilitate ongoing growth should also be as straightforward as possible, ideally without the need to interrupt power when adding or removing capacity, which also shouldn’t have an impact on the uninterruptible power supply equipment’s footprint.

Scalable modular UPS solutions

Fortunately modern, modular UPS technology that can meet these challenges is available. One popular implementation comprises a vertical racking UPS system that can be populated with one to five UPS modules of 100kVA each, the KOHLER PW 9500DPA. Hot-swappable power supplies allow UPS modules to be removed from or added to the rack to meet changing load requirements, without interrupting power to the load. If an uninterruptible power supply module does fail, hot-swappable UPS capacity minimises Mean Time to Repair (MTTR), significantly boosting availability.

The UPS design uses Decentralised Parallel Architecture (DPA), where each module contains all hardware and software essential for full UPS power system operation. No components are shared, so single points of failure are eliminated, ensuring very high power protection.

UPS power supply availability can be further improved by operating in N+1 redundancy mode. Five 100kVA UPS modules, for example, could provide fully redundant power for a 400kVA load. Adding uninterruptible power supply modules to the rack to increase capacity is called vertical scaling. Horizontal scaling adds further UPS capacity by paralleling up to six racking units, to support loads of up to 3MVA.

As the load increases, racks can be added with minimal disruption as each has just a 1.49 m2 footprint even while delivering a power density up to 335 kW/m2. Front and back clearances are also minimal, maximising the floor space available for revenue-earning servers. Near unity input power factor at all loads reduces input cable and fuse sizing, cutting cost for the electrical installation.

UPS battery sizing, and communications capability

These rack-mounted UPS power systems operate with external battery cabinets, allowing flexibility in UPS battery sizing. This is important for virtualised environments with a requirement to shut down a large number of virtual machines (VMs) in the event of an extended power failure. VMs can migrate from one server to another; knowing how many VMs are running on any host at a particular time becomes difficult. Additionally, shutting down large numbers of VMs simultaneously can cause contention for storage I/O, extending the time required for graceful shutdown. Having sufficient UPS battery autonomy to allow for these scenarios is, therefore, essential.

Comprehensive two-way UPS communications capability is also critical for power protection with the heavily-utilised servers in these environments. Simple Network Management Protocol (SNMP) is one popular platform- and vendor-independent solution. SNMP-enabled uninterruptible power supplies become network devices that can transmit and receive management variables across enterprise-wide networks. UPS power protection devices can be controlled and rebooted remotely across the network. If an extended power failure threatens UPS battery autonomy, information can be safeguarded while multiple servers and communications networks are automatically and gracefully shut down.


The continued penetration of data centre virtualisation is inevitable, given the IT efficiency advantages that it offers. However, data centre virtualisation invokes a dynamic, sometimes unpredictable but nearly always increased power demand from a dense population of heavily-utilised servers. Supporting these data centre operations with UPS power protection that is equally as responsive and flexible, while both essential and challenging, they can be achieved by sourcing the right UPS solutions now available from KUP one of the UK’s leading UPS suppliers.

If you require more information on any of our uninterruptible power supplies services or products please use our contact page or call 0800 731 3269

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