Measuring airflow for computing devices
Systems and methods for cooling computing devices in a data center and measuring airflow are disclosed. The computing devices have cooling fans that can have their fan speed set by management instructions. The devices are mounted in racks between cold aisles and hot aisles and are connected via network switches. The computing devices are oriented so that their cooling fans operate to exhaust waste heat to one side of the rack. Measurement instructions are sent to selected computing devices to cause them to go into a lower power state that reduces or stops computational work and reduces electrical power to the cooling fan so that the fan does not spin based on the electromotive force and can instead spin in an opposite direction based on ambient airflow caused by the difference in air pressure from the hot aisle to the cold aisle.
1. A method for measuring airflow for a plurality of computing devices, the method comprising:
positioning the plurality of computing devices on one or more racks, wherein each of the computing devices on each of the racks comprises a cooling fan configured to exhaust heat into a hot aisle, wherein each cooling fan comprises a rotor and a tachometer configured to measure the rotor's rotations;
connecting the computing devices via a network;
distributing computing workloads to the plurality of computing devices via the network;
performing work on the computing workloads on the plurality of computing devices;
sending a measurement instruction via the network to a selected one of the computing devices;
reducing power to the selected computing device's fan so that the fan is spinning due to ambient air flow rather than electrical motive force; and
reading RPM information from the selected computing device's fan's tachometer.
2. The method of claim 1 , further comprising refraining from performing work on the computing workloads on the selected one of the computing devices while reading the RPM information from the tachometer.
3. The method of claim 1 , further comprising:
calculating an airflow value based on a table of predetermined airflow values.
4. The method of claim 1 , further comprising sending the RPM information to a management application via the network.
5. The method of claim 1 , further comprising:
calculating an airflow value based on the RPM information and the selected computing device's fan's dimensions and pitch.
6. The method of claim 1 , wherein the selected one of the computing devices comprises a second fan, wherein the method further comprises turning off the second fan at least while reading the RPM information.
7. The method of claim 1 , further comprising periodically repeating the reading the RPM information step.
8. The method of claim 1 , further comprising:
detecting a malfunctioning computing device that is still capable of operating its fan and communicating via the network;
configuring the malfunctioning computing device to operate in a fan-only mode, wherein the fan-only mode comprises:
refraining from performing work on the computing workloads on the malfunctioning computing device until a repair occurs;
powering the malfunctioning computing device's fan to prevent hot air from traveling from the hot aisle through the malfunctioning computing device; and
periodically repeating the reducing power step and reading the RPM information step.
9. The method of claim 8 , wherein the configuring is performed by sending a firmware update to the malfunctioning computing device via the network.
10. The method of claim 1 , wherein the RPM information is used to calculate an air pressure differential between the hot aisle and a cold aisle.
11. The method of claim 1 , further comprising creating a map of airflow by repeating the measuring, reducing power, and reading steps for different computing devices in different locations at different times.
12. A non-transitory, computer-readable storage medium storing instructions executable by a processor of a computational device, which when executed cause the computational device to:
distribute computing workloads to a plurality of network-connected computing devices positioned on one or more racks in a data center, wherein the plurality of computing devices each have a cooling fan configured to exhaust heat into a hot aisle, wherein each cooling fan comprises a rotor and a tachometer configured to measure the rotor's rotations;
send one or more instructions via the network to a selected one of the computing devices, wherein the one or more instructions:
reduce fan power so that ambient air flow may turn the selected computing device's fan counter to the fan's normal spin direction; and
read RPM information from the selected computing device's fan's tachometer.
13. The non-transitory, computer-readable storage medium of claim 12 , wherein the one or more instructions cause the selected computing device to refrain from performing work on the computing workloads while reading the RPM information.
14. The non-transitory, computer-readable storage medium of claim 12 , further comprising instructions that when executed calculate an airflow value based on the RPM information read by the selected computing device.
15. The non-transitory, computer-readable storage medium of claim 12 , further comprising instructions that when executed create a map of airflow by repeating the measuring, reducing power, and reading steps at different times for different computing devices at different known locations within the data center.
16. A computing device comprising:
a controller configured to manage the computing device;
a plurality of processors in communication with the controller and configured to perform calculations;
a case containing at least the processors;
a first cooling fan configured during normal operation to spin in a first direction that draws cool air into the case and exhausts hot air out of the case in a particular direction; and
a first tachometer configured to measure rotation of the first cooling fan, wherein the controller is configured, in response to executing a measurement instruction, to:
reduce power to the first fan so that ambient air pressure may turn the first fan in a second direction counter to the first direction; and
read RPM information from the first tachometer.
17. The computing device of claim 16 , wherein the controller is further configured to cause the plurality of processors to refrain from performing work on the computing workloads while the controller is reading the RPM information.
18. The computing device of claim 16 , wherein the computing device further comprises a network adapter connected to a communications network, wherein the controller is further configured to send the RPM information via the network adapter to the network.
19. The computing device of claim 16 , wherein the computing device further comprises a second cooling fan and a second tachometer configured to measure rotation of the second cooling fan, wherein the controller is further configured to turn off the second cooling fan while reading the RPM information from the first tachometer.
20. The computing device of claim 19 , wherein the controller is further configured to turn off the first cooling fan while reducing power to the second fan and reading RPM information from the second tachometer caused by ambient air pressure.