Wednesday, July 30, 2008

Virtualization: Energy Efficiency vs Energy Sustainability

Virtualization is touted as a key solution in order to optimize datacenter efficiency. It allows clients to consolidate work onto fewer computers, increasing utilization, which can significantly reduce energy and maintenance bills and simplify their infrastructure.

It permits to evolve from computer systems using 5 percent to 12 percent of their capacity toward consolidated system running at 80% (remaining 20%: hypervisor + margin for manoeuvre).


Ok, now let’s have a look at what this means in number:

Before: (Source :"Epa report on server and data center energy efficiency")



After :
It’s a whopping increase from 1.4 Watts to 11.2 Watts. An 800% efficiency increase!!!!!

OK, now if you look at the big picture its only: an increase from 1.4% to 11.2% .. A really small increase of 9.8% . It’s still good but not the silver bullet the marketing drones want us to believe.

But the pitcture get a little darker if we start digging a little bit. Lets get some facts first, from Managing energy and server resources in hosting centers, we learn:
  • When server are idle they drawn 60% of their peak power consumption
  • The power comsumption is roughly linear with the load

Ok now, it means that if we move from an average 10% utilization ratio to a 90% (I roughly added 10% to the 80% for hypervisor related load), we end up drawing: 96% of the peak power consumption.
So far so good, let’s be bold and consider that we achieve an 8:1 consolidation ratio ( the reality is more around a 3:1 ratio) and we are still running the same hardware (while most of the time new , more powerfull, and ressource hungry hardware is deployed).
At the datacenter level it means we removed 7 servers out of 8 servers. An 87.5% reduction, which translate into an approximate reduction of power consumption of the servers by : 81.25 % not to forget that we can also reduce significantly the power , cooling and lightning consumption.


However, if you are a datacenter manager you don't want all this empty space (and unused servers) to go to waste (remember datacenter space is expensive). So we simply re-commissioned those servers for other task, lease them etc...

What do we end up with: a 36% power usage increase of the server’s power consumption of the datacenter + the rest. Roughly a 35% power consumption increase, BUT ! we increased the efficiency.


Now the big question where is the sustainability aspect in that?
Lets have a look at the sustainability definition :
"the quality of a state or process that allows it to be maintained indefinitely; the principles of sustainability integrate three closely interlinked elements—the environment, the economy, and the social system—into a system that can be maintained in a healthy state indefinitely."

Virtualization sustainability check :
  • Economy : Check ... More bangs for bukcs, revenue UP , shareholders happy
  • Social : Kind of Check ... We provide more services, customers happy
  • Environment : ... mm nope cannot find it, we are actually consumming more energy.
Result: Fail


Ok , now some will argue that you can turn off unused servers by using smart automation systems in order to reduce the environmental impact. Right .., why would a company would reduce its server ROI?
On top of that, here comes the savior buzzword : the cloud : Unused servers will be pushed into a cloud infrastructure so they can be used dynamically for other task .. No more waste