1. Are Low Power Server CPUs Worth the Cost?
Michael Fruchtman

2. 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

3. In this corner…

4. The Judges
vApus Mark I
Simulates a consolidated virtualization load
Meant for % 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

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

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

7. 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

8. Throughput and Response Time
Both graphs use the geometric mean.

9. 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

10. 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

11. Questions