We use EC2 a lot (on Project Clearwater - http://www.projectclearwater.org/ http://www.projectclearwater.org/), but I don't think we've ever seen significant le

We use EC2 a lot (on Project Clearwater - http://www.projectclearwater.org/ http://www.projectclearwater.org/), but I don't think we've ever seen significant levels of steal except on m1.small nodes. m1.small nodes expect up to 50% steal because you're explicitly only renting half the CPU. Check how /proc/cpuinfo compares with 1 ECU: http://aws.amazon.com/ec2/faqs/#What_is_an_EC2_Compute_Unit_and_why_did_you_introduce_it http://aws.amazon.com/ec2/faqs/#What_is_an_EC2_Compute_Unit_.... In fact, you can even see over 50% steal because the hypervisor steals from you if you're doing network-intensive work such as accepting TCP connections at a high rate (hundreds of new connections per second).