Amazon EC2 ’steals’ from you

by Michael Klatsky

As we implement more systems in the EC2 architecture, we are noticing a not so insignificant amount cpu cycles ’stolen’. What is a ’steal’ time? It is CPU time that is taken by the Xen hypervisor for something else other than your processes- from what I have read, other people’s processes. What we need to understand is how this affects performance. Does it truly matter? We have one virtual system that consistently has steal time of between 6-12%. That would mean that 6-12% of the CPU time we pay for is being used for instances other than our own. We will have to research this more to see what the true impact is on our systems, and if there is a way to mitigate it.