Green Clouds

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Nowadays the concept of Green Computing (or Green IT) is taking some relevance due to the widespread concerns about issues such as climate change, recycling, biodegradability, etc. In this post, we present the Green Computing focused on Cloud computing and virtualization. So we talk about energy consumption that implies a certain level of CO2 emissions.

It is estimated that the IT sector causes 2% of global CO2 emissions and in some articles it is said that the IT sector produces more carbon emissions than the world of aviation. For example some information published in Daily Telegraph talk about two Google searches produce the same CO2 as boiling a kettle.

Another important fact to keep in mind is that the IT sector is growing constantly, so this implies that energetic consumption is growing. It is an important data that produces more CO2 emissions. According to Greenpeace, world data centers to store Cloud computing services will triple emissions to the atmosphere in 2020. Currently there are several European researches to improve the consumption-performance ratio, especially for datacenters and supercomputers.

The most part of the pollution produced by Cloud computing is caused by world datacenters. Power usage effectiveness (PUE) is a measure of how efficiently is a computer datacenter using its power; specifically, how much of the power is actually used by the computing equipment (in contrast to cooling and other overhead). The overall average is 2, which means that for every watt used in running the equipment, has spent other one to keep cooled this.

Virtualization technology enables the consolidation of multiple workloads and always increases efficiency and most of them save energy on IT equipment, for example, using a smaller number of machines. Nevertheless, virtualization also produces some additional overheads and as a result the rest of the datacenter may be running less efficient. VM creation and VM migration is the most stand out overhead in Virtualization moreover, Virtualization technology use a new layer called hypervisor this means that a little high performance is lost. But virtualization overhead is insignificant in contrast to its advantages.

BSC (Barcelona Supercomputing Center) and UPC (UPC-Barcelona Tech) use EMOTIVE Cloud (software similar than OpenNebula and Openstack) to research about green virtualization. Virtualization requires high density datacenters. Remaining servers are running at higher power consumption levels but there are different ways to deal with this. Energy-aware Scheduling in Virtualized Data Centers is one example. This presents a Scheduler that uses a mathematical algorithm to manage Virtual Machines. Basically, the Scheduler makes a virtual machine consolidation in the minimum number of physical machines and the unused machines will be shutdowned. Scheduler manages the Virtual Machines migrating this to some physical machines to use the maximum possible performance of physical machines. And if there are some physical machines without any virtual machine and in idle mode, scheduler shutdown this server to consume less energy.

There are other solutions presented by others researches (1) (2) but the main idea is the same, the changes are in the idea of the scheduler algorithm. Nowadays commercial middlewares use a generic scheduler as backfilling that pack the VMs in the cluster nodes to reduce VM fragmentation and use the minimum number of physical servers.

Other aspects to considerate that it is important to understand the impact of Virtualization on Data Center Physical Infrastructure. The virtualization power savings can produce unexpected results and probably you need to upgrade power and cooling infrastructure to take advantage of the savings opportunity that virtualization offers. You need to worry about power and cooling when it is virtualizing. You may need additional cooling in some physical areas to improve the power efficiency. For example, it cools some areas dynamically depending on the load. Care should be taken to examine the impact on power and cooling because each data center virtualization is different.

A Cloud Admin

 

 

 

(1) CLUES is an energy management system for High Performance Computing (HPC) Clusters and Cloud infrastructures. – http://www.grycap.upv.es/clues/eng/index.php

(2)  Green Cloud Scheduler OpenNebula – http://opennebula.org/software:ecosystem:green_cloud_scheduler

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