Abstract:
In a method for designating cooling fan control management in a computing system, a processor causes one or more cooling fans to be managed by a first process, wherein the first process utilizes a first set of temperature sensors of a plurality of temperature sensors. A processor receives temperature data from a first set of temperature sensors. A processor determines a second process to manage the one or more cooling fans, based on the received temperature data from the first set of temperature sensors, wherein the second process utilizes a second set of temperature sensors of the plurality of temperature sensors.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of computing system temperature management, and more particularly to computing system cooling fan control. 
       BACKGROUND OF THE INVENTION 
       [0002]    Servers generate heat from the operation of electrical components, such as processors and hard drives. A temperature range, or rated temperature, is generally defined for each device or component. 
         [0003]    Cooling systems within a server or computer may include one or more cooling fans. For example, a computer may have a processor fan, a motherboard fan, a power supply fan, and/or a video card fan. Cooling systems are designed to dissipate heat within the computer system, so that the individual components continue to run at or below their maximum allowable temperature. 
         [0004]    Cooling systems often rely on temperature data from within the computer to control cooling fans or other cooling methods, such as water or air conditioned based cooling. One or more temperature sensors may be placed within a server or computer. The one or more temperature sensors may communicate temperature information to the cooling system controller. Temperature sensors are often available on computer motherboards and video cards. The most widely available temperature readings come from the chipset, the central processing unit (CPU), the ambient, or area surrounding the computer or server, and from the power circuitry. Modern CPUs can report their own internal temperature. Multi-core CPUs are often able to report temperatures from each single core. Self-monitoring, analysis and reporting technology (S.M.A.R.T.) is a monitoring system for computer hard disk drives to detect and report on various indicators of reliability. Using S.M.A.R.T., hard disk temperature can be read. 
       SUMMARY 
       [0005]    Aspects of embodiments of the present invention disclose a method, computer program product, and computing system for designating cooling fan control management in a computing system. A processor causes one or more cooling fans to be managed by a first process, wherein the first process utilizes a first set of temperature sensors of a plurality of temperature sensors. A processors receives temperature data from a first set of temperature sensors. A processor determines a second process to manage the one or more cooling fans, based on the received temperature data from the first set of temperature sensors, wherein the second process utilizes a second set of temperature sensors of the plurality of temperature sensors. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0006]      FIG. 1  depicts a diagram of a computing system in accordance with one embodiment of the present invention. 
           [0007]      FIG. 2  depicts a flowchart of the steps of a fan control program executing a stand-alone function within the computing system of  FIG. 1 , for determining cooling fan control management based upon temperature gradient data within a stand-alone server. 
           [0008]      FIG. 3  depicts a flowchart of the steps of a fan control program executing a chassis function within the computing system of  FIG. 1 , for determining cooling fan control management based upon temperature gradient data within a chassis-type server. 
           [0009]      FIG. 4  is a depiction of a computing device broken up into subsystems in accordance with one embodiment of the present invention. 
           [0010]      FIG. 5  is a block diagram of internal and external components of the server of  FIG. 1  in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable medium(s) having computer-readable program code/instructions embodied thereon. 
         [0012]    Any combination of computer-readable media may be utilized. Computer-readable media may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of a computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
         [0013]    A computer-readable signal medium may include a propagated data signal with computer-readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
         [0014]    Program code embodied on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
         [0015]    Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on a user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
         [0016]    Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0017]    These computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
         [0018]    The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0019]    The present invention will now be described in detail with reference to the Figures. 
         [0020]      FIG. 1  depicts a diagram of computing system  10  in accordance with one embodiment of the present invention for determining cooling fan control management based upon temperature gradient data.  FIG. 1  provides only an illustration of one embodiment and does not imply any limitations with regard to the environments in which different embodiments may be implemented. 
         [0021]    In the depicted embodiment, computing system  10  includes server  20 . Computing system  10  may also include a network, other servers, client computers, or other devices not shown. 
         [0022]    Server  20  may be a management server, a web server, laptop computer, tablet computer, netbook computer, personal computer (PC), or a desktop computer. In general, server  20  may be any electronic device that contains one or more cooling fan(s)  70  and a plurality of temperature sensors  60 . In one embodiment, server  20  may be a stand-alone server comprising a single computer. In another embodiment, server  20  may be a blade server, rack server, or other type of server in a chassis environment that contains multiple computers designed for rack mounting. Server  20  contains fan control program  30 , stand-alone function  40 , chassis function  50 , simple logic controller  80 , and complex logic controller  90 . 
         [0023]    Server  20  includes one or more cooling fan(s)  70 . Cooling fan(s)  70  are fans inside, outside, or attached to, a computer case and are used for active cooling. Cooling fan(s)  70  may draw cool air into the case from the outside, expel warm air from the inside, or move air across a heat sink to cool a particular component. Cooling fan(s)  70  may include processor fans, motherboard fans, power supply fans, video card fans, and/or other types of cooling fans. Server  20  contains one or more cooling fan(s)  70  which may be located within the case of server  20 , on the outside of the case of server  20 , or near various components (e.g., processor, memory, power supply, etc.) within the case of server  20 . In a chassis environment, additional cooling fan(s)  70  may be located on the chassis structure or on any of the blades, modules, or other components designed for rack mounting. 
         [0024]    Server  20  includes a plurality of temperature sensors  60 . Each of temperature sensors  60  can be any sensor or temperature identifying means capable of determining a temperature reading. Temperature sensors  60  are found in many computing devices and act to sound alarms when specified temperatures have been exceeded, and/or provide temperature information for fan control management. The most widely available temperatures are from the chipset, the CPU, the ambient, or area surrounding the computer or server, and from the power circuitry. The plurality of temperature sensors  60  may be located on the motherboard, power supply, video card, or at the inlet, outlet or other location within server  20 . In a chassis server embodiment, additional temperature sensors  60  may be located on the rack or chassis, and/or near various nodes or components within server  20 , such as a blade, module, or other component designed for rack mounting. Various components within server  20  may have independent temperature reporting capabilities. For example, modern central processing units (CPUs) can report their own internal temperature. Multi-core CPUs are often able to report temperatures from each single core. Self-monitoring, analysis and reporting technology (S.M.A.R.T.) is a monitoring system for computer hard disk drives to detect and report on various indicators of reliability, in the hope of anticipating failures. Using S.M.A.R.T., hard disk temperature can be read. 
         [0025]    Server  20  contains simple logic controller  80 . Simple logic controller  80  may be firmware, software, or circuitry. In one embodiment, simple logic controller  80  is a flexible service processor (FSP). A FSP is firmware that provides diagnostics, initialization, configuration, run-time error detection and correction. Simple logic controller  80  may run the simple logic process described below. In one embodiment, simple logic controller  80  runs a process that may require less energy or processing power to operate than complex logic controller  90 . 
         [0026]    Server  20  contains complex logic controller  90 . Complex logic controller  90  may be firmware, software, circuitry, a management controller or a thermal power management device (TPMD). A TPMD resides on the processor planar and is responsible for thermal protection of the processor cards. Complex logic controller  90  may run the complex logic process described below. In one embodiment, complex logic controller  90  runs a process that may require more energy or processing power to operate than simple logic controller  80 . 
         [0027]    Server  20  contains fan control program  30 . Fan control program  30  executes on server  20  and is capable of executing stand-alone function  40  and chassis function  50  to determine cooling fan control management based upon temperature gradient data. Temperature gradient data may include the direction and rate at which the temperature changes the most rapidly around a particular location. Temperature gradient data may also include changes in temperature between multiple temperature sensors. Fan control program  30  operates to receive temperature gradient data from a plurality of temperature sensors  60  within server  20 , and use the received temperature gradient data to determine whether a simple or complex logic controller is required to manage the one or more cooling fan(s)  70 . In one embodiment, fan control program  30  includes two functions: stand-alone function  40  and chassis function  50 . 
         [0028]    Stand-alone function  40  operates in an embodiment where server  20  is a stand-alone server or another single computing device. Stand-alone function  40  operates to receive temperature gradient data from a plurality of temperature sensors  60  within server  20 , and use the received temperature gradient data to determine whether simple or complex logic is required to manage the one or more cooling fan(s)  70 . 
         [0029]    In lower server resource utilization scenarios, the temperature gradient (i.e., which direction and at what rate the temperature changes the most rapidly around a particular location) or temperature change within a stand-alone server may be low. The change in temperature at the inlet and outlet (e.g., atmospheric air inlet and outlet, or cooling fluid inlet and outlet, etc.) of server  20  may be low enough that simple logic on a more energy efficient controller is all that is necessary to control the fan speed (or, e.g., coolant pump speed in an embodiment utilizing liquid cooling, etc.) and maintain acceptable internal component temperature. As the change in temperature at the inlet and outlet of server  20  increases, the simple logic may cause the fan speed to increase. If the temperature difference continues to increase, the simple logic may monitor subsystem sensors, such as processor or memory temperature sensors, in order to more effectively manage the temperature of the system. In one embodiment, when compared to the complex logic, the simple logic may monitor the plurality of temperature sensors  60  on a less frequent basis. In another embodiment, the simple logic may monitor a fewer number of the plurality of temperature sensors  60  as compared to the complex logic. 
         [0030]    Above a temperature threshold, or simple logic control threshold, stand-alone function  40  may transfer control of cooling fan(s)  70  to complex logic controller  90 . In an exemplary embodiment, complex logic controller  90  will only be turned on or otherwise activated when stand-alone function  40  determines that the simple logic control threshold within server  20  has been exceeded, and when the simple logic control threshold is no longer exceeded, simple logic controller  80  will resume control of cooling fan(s)  70 , and complex logic controller  90  will be shut down other otherwise deactivated. Deactivating complex logic controller  90  when not in use may allow for energy savings within server  20 . When complex logic controller  90  is managing cooling fan(s)  70  the complex logic may monitor more, as compared to the simple logic, or all of the plurality of temperature sensors  60  within server  20 . The complex logic may also monitor the plurality of temperature sensors  60  on a more frequent basis than the simple logic. In one embodiment, stand-alone function  40  will monitor the complex logic and move cooling fan management to the simple logic if any failures have been detected within the complex logic or mechanism that controls the complex logic. 
         [0031]    Chassis function  50  operates when server  20  is a multiple computer, or chassis-type server. Chassis function  50  operates to receive temperature gradient data, at the rack, node, and subsystem (e.g., processor, memory, etc.) levels, from a plurality of temperature sensors  60  within server  20 , and use the temperature gradient data to determine whether simple or complex logic is required to manage the one or more cooling fan(s)  70 . For example, at the rack level, chassis function  50  may receive temperature gradient data between the inlet and outlet of the chassis of server  20 . At the node level, chassis function  50  may receive temperature gradient data at the inlet and outlet of each node, or across multiple nodes. At the subsystem level, chassis function  50  may receive temperature gradient data between any of the following subsystem components: the inlet, outlet, processor, or memory. In low utilization scenarios, the temperature gradient and/or temperature change within the chassis may be low. The change in temperature among a plurality of temperature sensors  60  located on the chassis of server  20  may be low enough that a simple logic using chassis temperature gradient data is all that is necessary to control fan speed and maintain acceptable internal temperature among server  20  components. Above a certain temperature threshold, or chassis control threshold, a simple logic using both chassis and node temperature gradient data may be necessary to control the fan speed and maintain acceptable internal temperature. If node temperature gradient data indicates that individual nodes have temperatures above another temperature threshold, or node control threshold, the simple logic will receive subsystem temperature gradient data of affected nodes in order to assist the simple logic with fan control management. Similar to as described with regards to stand-alone function  40 , the simple logic in a chassis environment may monitor a plurality of temperature sensors  60  on a less frequent basis, or may monitor fewer of the plurality of temperature sensors  60  as compared to the complex logic. The monitoring frequency and the number of the plurality of temperature sensors  60  monitored may vary based on whether or not the chassis control or node control thresholds have been exceeded. 
         [0032]    Above another temperature threshold, or a simple logic control threshold, control of cooling fan(s)  70  may be transferred to complex logic controller  90 . In an exemplary embodiment, complex logic controller  90  may be shut down or deactivated when not in use. Shutting down or deactivating complex logic controller  90  may create energy savings in operating server  20 . When complex logic controller  90  is managing cooling fan(s)  70 , the complex logic may monitor more, as compared to the simple logic, or all of the plurality of temperature sensors  60  within server  20 . The complex logic may also monitor the plurality of temperature sensors  60  on a more frequent basis, as compared to the simple logic. In one embodiment, chassis function  50  will monitor the complex logic and move cooling fan management to the simple logic if any failures have been detected within the complex logic or mechanism that controls the complex logic. 
         [0033]    Fan control program  30  may have a number of thresholds. In the previous embodiments, a node control threshold, chassis control threshold, and simple logic control threshold have been discussed. Each threshold, or additional thresholds, may vary based upon the temperature constraints up the components and/or arrangement of components within the computing device. In one embodiment, each threshold may be determined by equating lab data at multiple power consumptions and at different cooling fan(s)  70  speeds against temperature gradient data, such as multiple inlet and outlet temperatures at different places, or across various subsystems. Threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the electrically erasable programmable read-only memory (EEPROM). EEPROM is a type of memory used in computing devices to store small amounts of data that must be saved when power is removed. 
         [0034]    Server  20  may include components as depicted and described in further detail with respect to  FIG. 5 . 
         [0035]      FIG. 2  depicts a flowchart of the steps of stand-alone function  40  of fan control program  30  executing within computing system  10  of  FIG. 1 , for determining cooling fan control management based upon temperature gradient data, in accordance with one embodiment of the present invention. Stand-alone function  40  of fan control program  30  may run when server  20  is a stand-alone or single computer server. 
         [0036]    In one embodiment, stand-alone function  40  of fan control program  30  will run as server  20  boots and periodically as the system runs. Stand-alone function  40  will determine whether cooling fan(s)  70  of server  20  should be controlled by simple logic controller  80  or complex logic controller  90 . In an exemplary embodiment, simple logic controller  80  consumes less energy during operation than complex logic controller  90 . 
         [0037]    In one embodiment, as server  20  boots, complex logic controller  90  may initially control cooling fan(s)  70 . If stand-alone function  40  receives temperature gradient data below a threshold (i.e., a simple logic control threshold), stand-alone function  40  may transfer cooling fan(s)  70  control to simple logic controller  80 . In addition, stand-alone function  40  may shut down, place into power save mode, or otherwise decrease the energy consumption requirements for complex logic controller  90  when the controller is inactive. 
         [0038]    In step  200 , stand-alone function  40  receives temperature gradient data. Temperature gradient data may include temperature information from a plurality of temperature sensors  60 . In one embodiment, the temperature gradient data received may be a change in temperature between temperature sensors located at the inlet and outlet of server  20 . In another embodiment additional temperature sensors may be monitored. 
         [0039]    In decision  210 , stand-alone function  40  determines, based on the temperature gradient data received (step  200 ), whether a simple logic control threshold has been exceeded. Stand-alone function  40  determines whether a simple logic control threshold has been exceeded by comparing the received temperature gradient data (step  200 ) to stored threshold information. Threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the electrically erasable programmable read-only memory (EEPROM). EEPROM is a type of memory used in computing devices to store small amounts of data that must be saved when power is removed. In one embodiment, the simple logic control threshold is a specific temperature at one or more of the plurality of temperature sensors  60 . For example, the simple logic control threshold may be a specific temperature at the temperature sensor located near the outlet of server  20 . In another embodiment, the simple logic control threshold is a change in temperature between two or more of the plurality of temperature sensors  60 . For example, the simple logic control threshold may be a specific change in temperature between temperature sensors  60  located near the inlet and outlet of server  20 . In yet another embodiment, the simple logic control threshold is a change in temperature at one of the plurality of temperature sensor  60  or between multiple of the plurality of temperature sensors  60  over a period of time, e.g., a rapid increase in temperature between the inlet and outlet temperature sensors  60 . 
         [0040]    If stand-alone function  40  determines that the simple logic control threshold has not been exceeded (decision  210 , no branch), stand-alone function  40  determines if cooling fan(s)  70  are being controlled by simple logic controller  80  (decision  240 ). Stand-alone function  40  may determine that cooling fan(s)  70  are being controlled by simple logic controller  80  (decision  240 ) by monitoring simple logic controller  80  for fan control activity. The simple logic may be firmware, software, or circuitry. In one embodiment, the simple logic may be a flexible service processor (FSP). A FSP is firmware that provides diagnostics, initialization, configuration, run-time error detection and correction. If stand-alone function  40  determines that cooling fan(s)  70  are being controlled by simple logic controller  80  (decision  240 , yes branch), the function is complete. The simple logic may manage control of cooling fan  70  according to the needs of the system. For example, below a certain temperature, the simple logic may monitor only the inlet and outlet of the stand-alone server system. As the change in temperature between the inlet and outlet increases, the simple logic may cause cooling fan(s)  70  to increase fan speed. At a designated temperature level or threshold, the simple logic may begin to monitor temperature sensors  60  located around different subsystems within server  20 . Such subsystems may include the processor, memory, or input/output (I/O) of server  20 . When this occurs, the simple logic may monitor gradients between different subsystems. For example, the simple logic may monitor the gradient between the inlet temperature sensor and the processor out temperature sensor, or between the processor out temperature sensor and the memory out temperature sensor. 
         [0041]    If stand-alone function  40  determines that cooling fan(s)  70  are not being controlled by simple logic controller  80  (decision  240 , no branch), stand-alone function  40  will transfer fan control to simple logic controller  80  (step  260 ). In one embodiment, stand-alone function  40  may transfer fan control to simple logic controller  80  by sending a command to initialize the simple logic. Once stand-alone function  40  has transferred fan control, the function is complete. 
         [0042]    In decision  210 , if stand-alone function  40  determines that the simple logic control threshold has been exceeded (decision  210 , yes branch), stand-alone function  40  determines if complex logic controller  90  is functioning properly (decision  220 ). Stand-alone function  40  may determine if complex logic controller  90  is functioning properly by monitoring the signals and/or failure notifications sent by complex logic controller  90 . The complex logic may be more complex than the simple logic. For example, the complex logic may monitor more temperature sensors  60 , and may monitor temperature sensors  60  on a more frequent basis than the simple logic. Complex logic controller  90  may be a microcontroller, a management controller, firmware, software, or circuitry. In one embodiment, the complex logic is controlled by a thermal power management device (TPMD). A TPMD resides on the processor planar and is responsible for thermal protection of the processor cards. In one embodiment, complex logic controller  90  may require more energy or processing power than simple logic controller  80 . 
         [0043]    If stand-alone function  40  determines that complex logic controller  90  is not functioning properly (decision  220 , no branch), stand-alone function  40  will determine if cooling fan(s)  70  are being controlled by simple logic controller  80  (decision  240 ). Stand-alone function  40  may determine that cooling fan(s)  70  are being controlled by simple logic controller  80  (decision  240 ) by monitoring simple logic controller  80  for fan control activity. If simple logic controller  80  is controlling cooling fan(s)  70  (decision  240 , yes branch), the function is complete. If simple logic controller  80  is not controlling cooling fan(s)  70  (decision  240 , no branch), stand-alone function  40  will transfer fan control to simple logic controller  80  (step  260 ). Once stand-alone function  40  has transferred control of cooling fan(s)  70 , the function is complete. 
         [0044]    If stand-alone function  40  determines that complex logic controller  90  is functioning properly (decision  220 , yes branch), stand-alone function  40  will determine if cooling fan(s)  70  are being controlled by complex logic controller  90  (decision  230 ). Stand-alone function  40  may determine that cooling fan(s)  70  are being controlled by complex logic controller  90  (decision  230 ) by monitoring simple logic controller  80  for fan control activity. If complex logic controller  90  is controlling cooling fan(s)  70  (decision  230 , yes branch), the function is complete. If complex logic controller  90  is not controlling cooling fan(s)  70  (decision  230 , no branch), stand-alone function  40  will transfer control of the one or more cooling fan(s)  70  to complex logic controller  90 . Once stand-alone function  40  has transferred control of cooling fan(s)  70  to complex logic controller  90 , the function is complete. 
         [0045]    In an exemplary embodiment, if stand-alone function  40  determines that neither complex logic controller  90 , nor simple logic controller  80  are functioning properly, stand-alone function  40  will cause cooling fan(s)  70  to ramp up to maximum speed and instruct other controllers present in server  20  to determine whether or not the system is to be shut down. 
         [0046]      FIG. 3  depicts a flowchart of the steps of chassis function  50  of fan control program  30  executing within computing system  10  of  FIG. 1 , for determining cooling fan control management based upon temperature gradient data, in accordance with another embodiment of the present invention. Chassis function  50  of fan control program  30  may run when server  20  is a chassis based server or blade server. 
         [0047]    In one embodiment, chassis function  50  of fan control program  30  will run when server  20  boots and periodically as computing system  10  operates. For example, chassis function  50  may run initially at boot, and then may run again every time a specified period of time has passed. Chassis function  50  will determine whether cooling fan(s)  70  of server  20  should be controlled by simple or complex logic controllers. In addition, chassis function  50  will determine whether the chassis, node, or subsystem (e.g., processor, memory) temperature gradient data should be used by simple logic controller  80  to control cooling fan(s)  70 . 
         [0048]    In one embodiment, as server  20  boots, complex logic controller  90  may initially control cooling fan(s)  70 . If chassis function  50  receives temperature gradient data below a threshold (i.e., a simple logic control threshold), chassis function  50  may transfer cooling fan(s)  70  control to simple logic controller  80 . In addition, chassis function  50  may shut down, place into power save mode, or otherwise decrease the energy consumption requirements for complex logic controller  90  when the controller is inactive. 
         [0049]    In step  300 , chassis function  50  receives chassis temperature gradient data. Chassis temperature gradient data may include temperature information from the plurality of temperature sensors  60  located on the chassis or rack. The plurality of temperature sensors  60  located on the chassis or rack may be located at the inlet and outlet of the chassis or rack, and may also be located elsewhere along the chassis or rack. In one embodiment, the chassis temperature gradient data received may be a change in temperature between temperature sensors located at the inlet and outlet of the chassis or rack. In another embodiment the chassis temperature gradient data may be received from additional temperature sensors on the chassis or rack. 
         [0050]    In decision  310 , chassis function  50  determines, using the chassis temperature gradient data received (step  300 ), whether a chassis control threshold has been exceeded. Chassis function  50  determines whether a chassis control threshold has been exceeded by comparing the received temperature gradient data (step  300 ) to stored threshold information. As previously discussed, threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the EEPROM. In one embodiment, the chassis control threshold is a specific temperature at one of the plurality of temperature sensors  60  located on the chassis. For example, the chassis control threshold may be a specific temperature at the temperature sensor located near the outlet of the chassis of server  20 . In another embodiment, the chassis control threshold is a change in temperature between multiple of the plurality of temperature sensors  60  located on the chassis. For example, the chassis control threshold may be a specific change in temperature between temperature sensors  60  located at the inlet and outlet of server  20 . In yet another embodiment, the chassis control threshold is a change in temperature at one or more of the plurality of temperature sensor  60  located on the chassis or between multiple of the plurality of temperature sensors  60  located on the chassis over a period of time, e.g., a rapid increase in temperature between the inlet and outlet temperature sensors for the chassis of server  20 . 
         [0051]    If chassis function  50  determines that the chassis control threshold is not exceeded (decision  310 , no branch), simple logic controller  80  will control cooling fan(s)  70  using received chassis temperature gradient data (see step  300 ). Chassis temperature gradient data may indicate the difference in temperature between the inlet and outlet temperatures of the chassis of server  20 . Similar to the simple logic discussed in  FIG. 2 , the simple logic may increase fan speed in response to increase temperatures in the chassis temperature gradient data. The simple logic may be firmware, software, or circuitry. In one embodiment, the simple logic may be controlled by a flexible service processor (FSP). A FSP is firmware that provides diagnostics, initialization, configuration, run-time error detection and correction. In another embodiment, the simple logic may be controlled by a chassis management module (CMM). A CMM is a module that configures and manages all installed chassis components. If simple logic controller  80  is not already controlling cooling fan(s)  70  using chassis temperature gradient data, chassis function  50  will transfer control of cooling fan(s)  70  to simple logic controller  80  and the function will be complete. Chassis function  50  may transfer control of cooling fan(s)  70  to simple logic controller  80  by sending a command to initialize the simple logic. 
         [0052]    In decision  310 , if chassis function  50  determines that the chassis control threshold has been exceeded (decision  310 , yes branch), then chassis function  50  receives node temperature gradient data (step  330 ). Chassis function  50  may determine that the chassis control threshold has been exceeded (decision  310 , yes branch) by comparing the received chassis temperature gradient data (step  300 ) to stored threshold information. As previously discussed, threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the EEPROM. Node temperature gradient data may include temperature information from the plurality of temperature sensors  60  located on or within the blades, nodes, or modules of server  20 . The plurality of temperature sensors  60  may be located at the inlet and outlet of each individual node and may also be located within individual nodes. In one embodiment, node temperature gradient data received may include changes in temperature between temperature sensors located at the inlets and outlets of individual nodes within server  20 . In another embodiment node temperature gradient data may be received from additional temperature sensors on or within each node. Node temperature gradient data may further include temperature sensor information from temperature sensors  60  located on or within the chassis. 
         [0053]    In decision  340 , chassis function  50  determines, based on the node temperature gradient data received (step  330 ), whether a node control threshold has been exceeded. Chassis function  50  may determine that the node control threshold has been exceeded (decision  340 , yes branch) by comparing the received node temperature gradient data (step  330 ) to stored threshold information. As previously discussed, threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the EEPROM. In one embodiment, the node control threshold is a specific temperature at one of temperature sensors  60 . For example, the node control threshold may be a specific temperature at the temperature sensor located near the outlet of a node within server  20 . In another embodiment, the node control threshold is a change in temperature between multiple of a plurality of temperature sensors  60 . For example, the node control threshold may be a specific change in temperature between temperature sensors  60  located near the inlet and outlet of the node within server  20 . In yet another embodiment, the node control threshold is a change in temperature at one or more of the plurality of temperature sensor  60  or between multiple of the plurality of temperature sensors  60 , e.g., a rapid increase in temperature between the node inlet and the node outlet temperature sensors  60 . Typically, a node control threshold value will be greater than a chassis control threshold value if the monitored threshold is of the same type. However, the node control threshold may examine different and additional sensors than the chassis control threshold, and may do so at a greater frequency. 
         [0054]    If chassis function  50  determines that the node control threshold has not been exceeded (decision  340 , no branch), simple logic controller  80  will control cooling fan(s)  70  using received node temperature gradient data (step  350 ). Node temperature gradient data may indicate the difference in temperature between the inlet and outlet temperatures of the various nodes within server  20 . In one embodiment, if simple logic controller  80  is unable to receive temperature gradient data from a particular node, possibly due to a temperature sensor read problem, simple logic controller may control cooling fan(s)  70  using temperature gradient data from nodes adjacent to the particular node. As previously discussed, the simple logic may be firmware, software, or circuitry. In one embodiment, the simple logic may be controlled by a flexible service processor (FSP). A FSP is firmware that provides diagnostics, initialization, configuration, run-time error detection and correction. In another embodiment, the simple logic may be controlled by a chassis management module (CMM). A CMM is a module that configures and manages all installed chassis components. If simple logic controller  80  is not already controlling cooling fan(s)  70  using node temperature gradient data, chassis function  50  will transfer control of cooling fan(s)  70  to simple logic controller  80  and the function will be complete. Chassis function  50  may transfer control of cooling fan(s)  70  to simple logic controller  80  by sending a command to initialize the simple logic. 
         [0055]    In decision  340 , if chassis function  50  determines that the node control threshold has been exceeded (decision  340 , yes branch), chassis function  50  receives subsystem temperature gradient data (step  352 ). Chassis function  50  may determine that the node control threshold has been exceeded (decision  340 , yes branch) by comparing the received node temperature gradient data (step  330 ) to stored threshold information. As previously discussed, threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the EEPROM. Subsystem temperature gradient data received may include temperature information from the plurality of temperature sensors  60  located on or within the computer components of server  20 , such as processors, memory, and I/O. In one embodiment, subsystem temperature gradient data received may include changes in temperature between temperature sensors located at the inlet and processor of individual nodes within server  20 . In another embodiment subsystem temperature gradient data may be between the memory and outlet of individual nodes within server  20 . Subsystem temperature gradient data may further monitor temperature sensors horizontally or vertically in order to compare temperature information across multiple nodes. In an exemplary embodiment, subsystem temperature gradient data will only be received for individual nodes that have node temperature gradient data above the node control threshold. 
         [0056]    In decision  354 , chassis function  50  determines, based on the subsystem temperature gradient data received (step  353 ), whether a simple logic control threshold has been exceeded. Chassis function  50  may determine that the simple logic control threshold has been exceeded (decision  354 , yes branch) by comparing the received subsystem temperature gradient data (step  352 ) to stored threshold information. As previously discussed, threshold information may be stored as data on a disk drive, flash drive, or alternatively may be stored to the EEPROM. In one embodiment, the simple logic control threshold is a specific temperature at one of temperature sensors  60 . For example, the simple logic control threshold may be a specific temperature at the temperature sensor located near a particular component within a node, such as the processor or memory. In another embodiment, the simple logic control threshold is a change in temperature between multiple of a plurality of temperature sensors  60 . For example, the simple logic control threshold may be a specific change in temperature between temperature sensors  60  located near the inlet and processor of a node, or near the memory and outlet of a node, within server  20 . In yet another embodiment, the threshold is a change in temperature at one or more of a plurality of temperature sensor  60  or between multiple of a plurality of temperature sensors  60 , e.g., a rapid increase in temperature between the processor sensor and memory sensor within a node. Typically, a simple logic control threshold value will be greater than a chassis control threshold value if the monitored threshold is of the same type. However, the simple logic control threshold may examine different and additional sensors than the chassis control threshold, and may do so at a greater frequency. 
         [0057]    If chassis function  50  determines that the simple logic control threshold is not exceeded (decision  354 , no branch), simple logic controller  80  will control cooling fan(s)  70  using received subsystem temperature gradient data (step  356 ). As previously discussed, the simple logic may be controlled by firmware, software, or circuitry. In one embodiment, the simple logic may be a flexible service processor (FSP). A FSP is firmware that provides diagnostics, initialization, configuration, run-time error detection and correction. In another embodiment, the simple logic may be controlled by a chassis management module (CMM). A CMM is a module that configures and manages all installed chassis components. If simple logic controller  80  is not already controlling cooling fan(s)  70  using subsystem temperature gradient data, chassis function  50  will transfer control of cooling fan(s)  70  to simple logic controller  80  and the function will be complete. Chassis function  50  may transfer control of cooling fan(s)  70  to complex logic controller  90  by sending a command to initialize the simple logic. 
         [0058]    If chassis function  50  determines that the simple logic control threshold has been exceeded (decision  354 , yes branch), chassis function  50  will cause complex logic controller  90  to control cooling fan(s)  70  (step  360 ). Similar to  FIG. 2 , the complex logic may be more complex than the simple logic. For example, the complex logic may monitor additional temperature sensors of the plurality of temperature sensors  60 , and may monitor temperature sensors  60  on a more frequent basis in order to control the one or more cooling fan(s)  70 . Complex logic controller  90  may be a microcontroller, a management controller, firmware, software, or circuitry. In one embodiment, the complex logic is controlled by a thermal power management device (TPMD). A TPMD resides on the processor planar and is responsible for thermal protection of the processor cards. In one embodiment, complex logic controller  90  may require more energy or processing power than simple logic controller  80 . 
         [0059]    Similar to  FIG. 2  (not shown in  FIG. 3 ), if chassis function  50  determines that complex logic controller  90  is not functioning properly, chassis function  50  will transfer control of cooling fan(s)  70  to simple logic controller  80 , if simple logic controller  80  is not already controlling cooling fan(s)  70 , and cause simple logic controller  80  to control cooling fan(s)  70  using node temperature gradient data. Chassis function  50  may determine that complex logic controller  90  is not functioning properly by monitoring the signals and/or failure notifications sent by complex logic controller  90 . Once simple logic controller  80  has control of cooling fan(s)  70 , the function is complete. 
         [0060]    In an exemplary embodiment, if chassis function  50  determines that neither complex logic controller  90 , nor simple logic controller  80  are functioning properly, chassis function  40  will cause cooling fan(s)  70  to ramp up to maximum speed and instruct other controllers present in server  20  to manage whether or not the system is to be shut down. 
         [0061]      FIG. 4  depicts internal components  400  within a system in a computing device, such as server  20 , broken up into subsystems in accordance with one embodiment of the present invention. In a stand-alone server, internal components  400  may comprise server  20 . If server  20  is a chassis server, internal components  400  may comprise an individual node, module, or blade mounted within the chassis. 
         [0062]    In the depicted embodiment, internal components  400  breaks up the hardware components of internal components  400  into a processor subsystem  420 , a memory subsystem  440 , and an input/output (I/O) subsystem  460 . Each respective subsystem contains the hardware components that represent the processor, memory, and I/O (see  FIG. 5  for a more in depth discussed of hardware components). Internal components  400  may also include a plurality of temperature sensors  60 , such as inlet sensor  410 , processor out-sensor  430 , memory out-sensor  450 , outlet sensor  470 , and other temperature sensors (not shown). At least one airflow inlet is present in proximity to inlet sensor  410 , and at least one airflow outlet is present in proximity to outlet sensor  470 . In addition, cooling fan(s)  70  may be located on or in proximity to internal components  400 . 
         [0063]    In the depicted embodiment, the hardware components that make up internal components  400  have been organized in such a way that air will enter through the inlet, travel across inlet sensor  410 , processor subsystem  420 , processor out-sensor  430 , memory subsystem  440 , memory out-sensor  450 , I/O subsystem  460 , outlet sensor  470 , and then exit through the outlet. As has been previously discussed, simple logic controller  80  may control cooling fan(s)  70  using subsystem temperature gradient data (see both FIG.  2 —Stand-alone Function, and FIG.  3 —Chassis Function). In the depicted embodiment, subsystem gradient data may include temperature changes between inlet sensor  410  and processor out-sensor  430 , between processor out-sensor  430  and memory out-sensor  450 , or between memory out-sensor  450  and outlet sensor  470 . In another embodiment, subsystem gradient data may include changes in one or more temperature sensor readings, as previously discussed. It should be recognized, that hardware components, subsystems, cooling fan(s)  70  and temperature sensors  60  may be rearranged and reorganized as desired. Additional hardware components and sensors (not shown) may exist on or within internal components  400 . 
         [0064]      FIG. 5  depicts a block diagram of components of server  20  in accordance with an illustrative embodiment of the present invention. It should be appreciated that  FIG. 5  provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environment may be made. 
         [0065]    Server  20  includes communications fabric  502 , which provides communications between computer processor(s)  504 , memory  506 , persistent storage  508 , communications unit  510 , and input/output (I/O) interface(s)  512 . Communications fabric  502  can be implemented with any architecture designed for passing data and/or control information between processors (such as microprocessors, communications and network processors, etc.), system memory, peripheral devices, and any other hardware components within a system. For example, communications fabric  502  can be implemented with one or more buses. 
         [0066]    Memory  506  and persistent storage  508  are computer-readable storage media. In this embodiment, memory  506  includes random access memory (RAM)  514  and cache memory  516 . In general, memory  506  can include any suitable volatile or non-volatile computer-readable storage media. 
         [0067]    Fan control program  30 , stand-alone function  40 , chassis function  50 , simple logic controller  80 , and complex logic controller  90  are stored in persistent storage  508  for execution by one or more of the respective computer processors  504  via one or more memories of memory  506 . In this embodiment, persistent storage  508  includes a magnetic hard disk drive. Alternatively, or in addition to a magnetic hard disk drive, persistent storage  508  can include a solid state hard drive, a semiconductor storage device, read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, or any other computer-readable storage media that is capable of storing program instructions or digital information. 
         [0068]    The media used by persistent storage  508  may also be removable. For example, a removable hard drive may be used for persistent storage  508 . Other examples include optical and magnetic disks, thumb drives, and smart cards that are inserted into a drive for transfer onto another computer-readable storage medium that is also part of persistent storage  508 . 
         [0069]    Communications unit  510 , in these examples, provides for communications with other data processing systems or devices. In these examples, communications unit  510  includes one or more network interface cards. Communications unit  510  may provide communications through the use of either or both physical and wireless communications links. Fan control program  30 , stand-alone function  40 , chassis function  50 , simple logic controller  80 , and complex logic controller  90  may be downloaded to persistent storage  508  of server  20  through communications unit  510  of server  20 . 
         [0070]    I/O interface(s)  512  allows for input and output of data with other devices that may be connected to computing system  10 . For example, I/O interface  512  may provide a connection to external devices  518  such as a keyboard, keypad, a touch screen, and/or some other suitable input device. External devices  518  can also include portable computer-readable storage media such as, for example, thumb drives, portable optical or magnetic disks, and memory cards. Software and data used to practice embodiments of the present invention, e.g., fan control program  30 , stand-alone function  40 , chassis function  50 , simple logic controller  80 , and complex logic controller  90 , can be stored on such portable computer-readable storage media and can be loaded onto persistent storage  508  via I/O interface(s)  512 . I/O interface(s)  512  also connect to a display  520 . 
         [0071]    Display  520  provides a mechanism to display data to a user and may be, for example, a computer monitor. 
         [0072]    The programs described herein are identified based upon the application for which they are implemented in a specific embodiment of the invention. However, it should be appreciated that any particular program nomenclature herein is used merely for convenience, and thus the invention should not be limited to use solely in any specific application identified and/or implied by such nomenclature. 
         [0073]    The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.