The hidden challenges of virtualisation

By Craig Gob*
Wednesday, 07 July, 2010

For all its advantages, virtualisation brings some unique challenges. Data centre power consumption may be lower but each server draws more power; and while there are fewer servers, each one becomes more critical than ever. Each beneficial change has flow-on effects that need to be managed. The good news is that there are practical and affordable ways to address all these challenges, and improve data centre efficiency in the process. Who better to explain than Eaton’s Craig Gob*.

On an un-virtualised platform, the average server CPU (central processing unit) runs at 10 to 15% of capacity. With virtualisation, it jumps to 70 to 80%. The higher the CPU utilisation, the higher the power consumption per server. This makes it essential for the power distribution system in a virtualised environment to provide enough in-rack power for high-density servers.

However, users can increase the density of enclosure-level power protection and distribution. Enclosure-based power modules can distribute up to 36 kW in only a few standard units (Us) of rack space. The newest generation of enclosure-based power distribution units (PDUs) distributes power to up to 45 receptacles for a range of power densities including standard, mid, high and ultra.

Traditionally, data centre managers could plan for up to 100 watts of power consumption per U of rack space. A full rack of equipment averaged 3 to 4 kW of power. With today’s blade servers that figure has escalated to 600 to 1000 watts per U, and growing.

It’s typical to find there are not enough circuits to support these high-density racks, or enough power drops to add more loads.

This can be solved by creating a power sub-distribution capability. Instead of running individual cable drops from large UPSs and PDUs to each rack, run higher powered sub-feed circuits to an intermediate remote power panel, power distribution rack or rackmounted power distribution device - and from there to enclosures.

Virtualisation often results in a cluster of high-density racks in a data centre designed for lower-density racks. In these cases, the capacity of the existing centralised UPS can become a bottleneck, especially as redundancy becomes more important.

To avoid this problem, look for enclosure-based UPS systems with power densities of 2 kW or more per U, and which can be deployed in a variety of system architectures.

On-demand migration of applications requires new levels of visibility into how IT applications affect power, and vice versa. Is the IT equipment that runs the most important applications receiving computer-grade power? If you move processing-intensive applications, will you overload a branch circuit? Which rack has enough power to accommodate new virtualised servers and their applications?

The answer is to provide 24/7 power quality metering, monitoring and management at the branch circuit level.

Power conditions must also be aligned with the shifting applications being supported. This calls for a monitoring system that unifies IT and facilities information so that organisations can easily see when abnormal conditions arise and which business services are at risk.

Server virtualisation enables a data centre to meet its service level agreements with fewer physical servers, which in turn results in dramatic savings in energy and footprint. However, to successfully implement a virtualisation project, IT teams need to account for some new realities such as dynamic changes in power demands, higher server and rack power densities, and the need to protect applications with sufficient UPS capacity.

* Craig Gob is the Managing Director ANZ, Eaton Industries. Gob joined Eaton in Australia earlier this year and has more than 15 years of career experience with the company having held several senior management positions with Eaton in the United States.

Most recently, he served as Regional Vice President and Director of Sales in Dallas, Texas. In this role, he developed and implemented Eaton’s go-to-market strategies for the company’s industrial and data centre infrastructure markets in the Southwestern United States.

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