Load balancing with VMware DPM (Dynamic Power Management).

Our original involvement in “The Cloud” came from becoming involved with the Cassatt Collage product, now called “Active Response”. Collage was all about shutting down and powering up servers based on demand. The product integrates with VMware and Xen as well as physical servers and is very flexible.

If however you are a pure VMware shop, or have less complex needs, then the new Dynamic Power Management (DPM) functionality that VMware has in the pipeline is probably a good place to start looking.

The basic idea is that a machine that is turned off uses less electricity and needs less air conditioning than a powered on server. So if you can turn servers on and off as required, then you can potentially save your business a considerable amount in electricity and air conditioning costs. Your mileage may vary, but savings in the region of 55% are being quoted.

Below is a video from Cody Bunch in the USA, which shows an example of this all happening, including showing the monitoring of the power usage by servers. It shows a ‘typical‘ work day in a server room, low use before and after hours. In this example we start with a single VMware ESX host, and all the virtual servers running on it. As load increases, new ESX hosts are powered up and virtual machines “VMotion-ed” to the new servers to balance the load. This continues until all four ESX host servers are running. Then at the end of the day, the extra servers are shut down as CPU load drops.

For those of you reading this in a RSS feader the video is available at http://uk.youtube.com/watch?v=7CbRS0GGuNc .
*** Warning, Cody put a rather loud musical soundtrack on this video, so I suggest turning down your speakers before you hit play.

The video is a great visualisation of what an internal cloud infrastructure might need to respond like. Without any human intervention, this example configuration responds to increased load. This is really powerful as it means that as well as saving money in electricity, it is protecting your users from performance issues that might occur if a human had to be part of the process of balancing the load.

Of course, the limitation to DPM (other than being a test feature at this time), is that it supports only part of your infrastructure. Specifically, it only is able to manage VMware virtual machines and ESX host servers. If you have a more complex (some might say normal) infrastructure with a mix of virtualisation platforms (KVM, Xen, etc.) along with physical servers then DPM may not be right for you. Cassatt or OpenQRM might be the answer you are looking for.