Are Low Power Server CPUs Worth the Cost? Michael Fruchtman

Power Usage of a Small Server Setup Example: Given 4 servers Server consumes 250W each at 60% United States 10-11 amps, 1200W (safety margin) Cost $300 a year Europe 5amps (higher voltage), but amps cost more $500 a year Also - carbon footprint

In this corner…

The Judges vApus Mark I Simulates a consolidated virtualization load Meant for 90-100% load comparisons Good for HPC, not good for servers Servers operate at 30-60% Solution: Reduce the simulated machines by half Simulate load of an OLAP database (4 vCPUs), OLTP database (4 vCPUs), and 2 VMs Both CPUs can handle double this load Measure response time, throughput, and power usage

Idle Power Usage At idle PCU shuts down 5 cores Reduce clock speed No difference at idle

Under Load At average power use Throughput X5670 considerably more 25-60W more Throughput L5640 took 66 minutes X5670 took 59 minutes

Total Power Use Even power usage Race to idle L5640 and X5670 on balanced X5670 consumed 20Wh more Race to idle X5670 able to race to idle and shutdown Idle power consumption makes up for higher use

Throughput and Response Time Both graphs use the geometric mean.

Addition Statistics L5640 at Balanced to High Perf X5670 69% of throughput,76% longer response time, but 91% of power consumption L5640 at Balanced to Balanced X5670 76% of throughput, 34% longer response time, but 97% of power consumption Not a good deal if you can afford it X5670 costs $900 more than L5640 Adds only $200 a year in power cost

Any Advantages? Caps maximum power draw Range of X5670 is higher With L5640 one knows maximum draw of a server over time due to cap of 60W Data centers have penalties if one exceeds the power allowance Low power CPUs save power, but not energy

Questions