Free Cooling: the Server Side of the Story

The Supermicro "PUE-Optimized" Server

We tested the Supermicro Superserver 6027R-73DARF. We chose this particular server for two main reasons: first, it is a 2U rackmount server (larger fans, better airflow) and secondly, it was the only PUE optimized server with 16 DIMMs. Many applications are more memory capacity than CPU limited, so a 16 DIMM server is more desirable to most of our readers than an 8 DIMM server.

On the outside, it looks like most other Supermicro servers, with the exception that the upper third of the front is left open for better airflow. This in contrast with some Supermicro servers where the upper third is filled with disk bays.

This superserver has a few features to ensure that it can can cope with higher temperatures without a huge increase in energy consumption. First of all, it has an 80 Plus Platinum power supply. A platinum PSU is not exceptional anymore: almost every server vendors offers at least the slightly less efficient 80 Plus Gold PSUs. Platinum PSUs are the standard for new servers, DELL and Supermicro even started offering 80 Plus Titanium PSUs (230V). 

Nevertheless, these Platinum PSUs are pretty impressive: they offer better than 92% efficiency from 20% to 100% load.

Secondly, it uses a spreadcore design. Here, the CPU heatsinks do no obstruct each other: the air flow will go over them in parallel.

Three heavy duty fans blow over a relatively simple motherboard design. Notice that even the heatsink on the 8W Intel PCH (602J chipset) is also in parallel with the CPU heatsinks. Indeed, the PCH heatsink will get an unhindered airflow. Last but not least, these servers come with specially designed air shrouds for maximum cooling.

There is some room for improvement though. It would be great to have a model with 2.5-inch drive bays. Supermicro offers a 2,5'' HDD conversion tray (MCP-220-00043-0N), but a native 2.5-inch drive bay model would give even better airflow and serviceability. 

We would also like an easier way to replace the CPUs. The screws of the heatsink tend to wear out quickly. But that is mostly a problem of a lab testing servers, less a problem of a real enterprise.