Abstract:
Power resource allocation at a chassis that supports plural server information handling systems is enhanced with modifications to power consumption by plural cooling fans based upon available power resources. As available power decreases, at least some of the cooling fans operate at reduced speeds for a given thermal condition to consume less power. In one embodiment, a maximum allowed cooling fan speed is set with a delta value over the fan speed of one or more other cooling fans, such as a delta over the lowest commanded cooling fan speed of the chassis.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates in general to the field of information handling system power management, and more particularly to information handling system dynamic fan power management. 
         [0003]    2. Description of the Related Art 
         [0004]    As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems. 
         [0005]    Information handling systems are built from a variety of components that consume electrical power and produce heat as a byproduct of their operations. Generally, information handling systems include some sort of active and/or passive thermal energy management to prevent excessive temperatures that can lead to system failure. Typical active thermal energy management includes attaching heat sinks to components that generate thermal energy and passing a cooling airflow over the heat sinks to remove the thermal energy from the information handling system. Generally, the larger the surface area of the heat sink and the greater the airflow rate used in an active thermal energy management system the greater the amount of thermal energy that is removed from the information handling system. 
         [0006]    Although adequate thermal energy management for an information handling system is generally maintained with powerful enough cooling fans, other factors constrain the size of cooling fans available for a particular information handling system. One factor is the size of the housing of the information handling system. Larger housings generally have less impedance to airflow and more size to include larger cooling fans that generate greater cooling airflow. In contrast, smaller housings have greater impedance to airflow so that a given cooling fan tends to have less effectiveness than in a larger housing. In addition, smaller housings have less room for heat sinks so that less heat sink surface area generally leads to less effective thermal transfer for a given cooling airflow. Another constraint on cooling fan size and the number of cooling fans included in a housing is the power consumption by the cooling fans. Typically, an information handling system has a power supply with a maximum power output. In some instances cooling fan power draw varies between 5% and 25% of available power depending upon the thermal conditions within an information handling system housing. 
         [0007]    Thermal energy management in multi-node information handling systems can present a complex problem due to the large variation in thermal conditions within an information handling system rack or other type of multi-node chassis. Multi-node server information handling systems often are designed to have a high density to increase the processing capability of systems deployed in valuable data center space. An information handling system rack may include a large number of server information handling systems in a dense arrangement that share power and cooling resources under the control of a chassis management controller (CMC). Thermal conditions within a rack can vary considerably based upon workload at different information handling systems. One difficulty with shared power and cooling resources is that a component or server node cooling request can result in a power draw for a cooling fan that causes a non-linear performance per Watt behavior for a rack. Essentially, a single component or server node can cause a much larger cooling fan speed response than is required by other components or nodes, which results in a relatively large cooling fan power draw that fails to provide a linearly-related decrease in thermal conditions within the rack. Another problem is that a component or server node cooling fan request can draw power that exceeds the power output of a rack power supply, resulting in power supply shutdown or performance impacts on other component or server node operations, such as CPU throttling or other component thermal management actions. In some systems, a fan speed maximum input to a single fan can map to other fans to go full speed resulting in high power consumption with relatively little improvement in thermal transfer from the system. 
       SUMMARY OF THE INVENTION 
       [0008]    Therefore a need has arisen for a system and method which controls cooling fan power consumption while providing effective cooling for thermal management of one or more information handling systems. 
         [0009]    In accordance with the present invention, a system and method are provided which substantially reduce the disadvantages and problems associated with previous methods and systems for information handling system power and thermal management. Cooling fan operating parameters adjust based upon power consumption to provide balanced performance for information handling system servers that share power resources of a chassis. 
         [0010]    More specifically, a chassis supports plural server information handling system sleds with shared power and cooling resources. A fan controller commands fan speeds for cooling server information handling system sled components based upon sensed thermal conditions and a fan speed configuration. The fan speed configuration is selected based upon power resource availability at the information handling system chassis. If power consumption exceeds a threshold associated with restrictions on processing capabilities, such as throttling of processors, a fan speed configuration applies that conserves power used by cooling fans. A reduced power fan speed configuration caps a maximum fan speed commanded at one or more cooling fans to a fan speed of less than an available maximum fan speed. In one embodiment, the maximum allowed fan speed is determined from a delta over various other commanded fan speeds, such as a delta plus the minimum commanded fan speed, a delta plus a median or mean fan speed, or from other values, such as the relative thermal state of the information handling system chassis considered as whole. 
         [0011]    The present invention provides a number of important technical advantages. One example of an important technical advantage is that fan speed behavior is based upon system power consumption to provide improved overall system performance on a per Watt basis. Although reduced fan speed may cause some components to operate in degraded modes, such as with the throttling of CPUs to produce less thermal energy, other components that have not achieved a thermal constraint will have power available for normal operations. Additional constraints on fan speed behavior may be applied to improve performance, such as by relating fan speed settings relative to each other and restricting fan speeds against acoustic constraints. For instance, a maximum fan speed delta between one or more cooling fans prevents a thermal hotspot within a housing from having an undue impact on power consumption. Multi-node systems that share power between cooling fans and processing components achieve a balance in power consumption and thermal management for improved overall processing at a given power consumption. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element. 
           [0013]      FIG. 1  depicts a side cutaway view of an information handling system having a chassis supporting plural server information handling system sleds with cooling by plural fan speed configurations; 
           [0014]      FIG. 2  depicts a block diagram of a fan controller having plural fan speed configurations to determine cooling fan speeds based upon power consumption; and 
           [0015]      FIG. 3  depicts a flow diagram of a process for setting cooling fan speeds based upon available chassis power resources. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    An information handling system sharing power and cooling resources manages power consumption by cooling resources to improve system processing performance relative to consumed power. For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components. 
         [0017]    Referring now to  FIG. 1 , a side cutaway view depicts an information handling system  10  having a chassis  12  supporting plural server information handling system sleds  14  with cooling by plural fan speed configurations. In the example embodiment depicted by  FIG. 1 , information handling system  10  chassis  12  is a rack that vertically stacks server information handling system sleds  12 , each of which includes a CPU  16  and memory  18  disposed on a motherboard  20  for processing information. In alternative embodiments, alternative physical configurations of server information handling system sleds  14  may be used, such as a blade configuration having horizontally stacked blade modules. Server information handling system sleds  14  share power resources, such as one or more power subsystems  22 , that provide regulated direct current power used by CPUs  16 , memory  18  and other components disposed in chassis  12  and server information handling system sleds  14 . For example, power subsystems  22  provide power to plural cooling fans  24  that provide a cooling airflow through chassis  12  to remove excess thermal energy generated by components disposed in chassis  12 . 
         [0018]    During operation, cooling fans  24  operate at varying speeds to produce varying amounts of cooling airflow in response to thermal conditions within chassis  12 . For instance, thermal sensors  26  are distributed throughout chassis  12  to measure temperatures and report the temperatures to a fan controller  28 . Fan controller  28  applies the sensed thermal conditions to command fan speeds at each of plural cooling fans  24 . Fan controller  28  commands greater fan speeds for cooling fans  24  that are proximate to increased thermal energy and lesser fan speeds for cooling fans  24  that are proximate to reduced thermal energy. As an example, if a server information handling system sled  14  has a relatively high load at a CPU  16 , increased processing cycles will increase power consumption from power subsystem  22  and, as a consequence, increase thermal energy output from the CPU  16  as a byproduct of the increased power consumption. The example embodiment depicted by  FIG. 1  has fan controller  28  exercising centralized control over fan speeds of plural cooling fans  24 , however, in alternative embodiments, fan controller  28  may have logic distributed between various processing and memory resources of chassis  12 . For example, a chassis management controller (CMC)  30  may exercise varying degrees of management control over fan speeds in cooperation with baseboard management controllers (BMCs)  32  distributed at the server information handling system sleds  14 . 
         [0019]    A difficulty that arises with increased fan speeds used to remove increased thermal energy associated with increased processor loads is that available power from power subsystem  22  may reach a limit that reduces power available for performing processing functions. In one example embodiment, power used by cooling fans  24  to remove excess thermal energy can vary from between 5% of the power available from power subsystem  22  to up to 25% of power available. In some instances, power conservation techniques are applied to processing components in order to ensure that adequate power is available for cooling fans  24 , resulting in unexpected and nonlinear system performance To minimize the impact of power consumption by cooling fans  24  on system performance, fan controller  28  implements a variety of power and thermal management constraints that balance system performance against thermal and power limits. Under conditions where power subsystem  22  approaches power supply limits, fan controller  22  analyzes the overall thermal state at chassis  12  to adjust cooling fan  24  speeds so that power is preserved for processing components to operate, even if some of the processing components have to operate under constraints that limit generation of thermal energy. 
         [0020]    Fan controller  28  improves overall system efficiency by reducing fan speeds that are associated with less efficient thermal energy transfer. For example, a maximum fan speed in a system having relatively high impedance to cooling airflow does not produce substantial improvements in thermal energy transfer relative to a fan speed of 85% of the maximum fan speed. By setting a maximum fan speed of 85% of an available maximum fan speed, fan controller  28  reduces power consumption of the cooling fan without substantially impacting thermal energy transfer. If a slower fan speed for a cooling fan  24  impacts thermal energy transfer, then components cooled by the restricted cooling fan  24  may have to operate in a reduced power consumption mode to reduce thermal energy created proximate to the restricted cooling fan  24 , however, other portions of chassis  12  will have power available that would otherwise have been inefficiently consumed by the restricted cooling fan  24 . Fan controller  28  imposes restrictions on cooling fan maximum speeds at a power consumption threshold in a number of possible ways, such as setting fan speed behavior with fan speed configurations based upon power consumption, acoustic limits and performance per Watt requirements, setting a static fan speed limit based on information handling system  10  configuration, fan count, fan location, etc. . . . , and/or setting a maximum fan speed based on difference from other commanded fan speeds. 
         [0021]    Referring now to  FIG. 2 , a block diagram depicts a fan controller  28  having plural fan speed configurations  34  to determine cooling fan speeds based upon power consumption. Fan controller  28  has a processor  36  that executes instructions stored in a memory  38  to generate commands for determining cooling fan speeds of plural cooling fans  24  in a chassis  12 . In various embodiments, instructions of fan controller  28  may be distributed across plural processors and memory of chassis  12 , such as CMC  30 , BMCs  32  and cooling fans  24 . Fan controller  28  receives thermal sensor measurements from thermal sensors  26  and power consumption information from power supply  22  and applies sensed thermal conditions and available power to a fan speed configuration  34  to determine a fan speed to command for each of the plural cooling fans  24 . Essentially, fan controller  28  attempts to set fan speeds in response to the overall chassis thermal state that will efficiently use available power for cooling while preserving at least some power allocated for cooling fan use to instead support processing component operations. To achieve this, fan controller  28  selects one of plural fan speed configurations  34  based upon the amount of available power from power supply  22 . For example, as the available power of power supply  22  is consumed, fan speed configurations  34  are used that reduce power consumption by cooling fans  24 . A fail safe module  40  overrides restrictions on fan speeds of cooling fans  24  if thermal conditions become excessive to ensure that damage does not occur to components disposed in chassis  12 . 
         [0022]    In one embodiment, fan controller  28  applies a fan speed configuration  34  at low power utilization rates of power supply  22  that allows commands to cooling fans  24  to run at a maximum allowable speed. Once fan controller  28  detects a power consumption threshold for power consumed from power supply  22 , a reduce power consumption fan speed configuration is selected for determining fan speeds at sensed thermal conditions. In one embodiment, a static maximum speed of less than the available maximum speed is applied for one or more of the plural cooling fans  24 . A static fan speed cap might also be applied in conditions where a maximum acoustics is desired since the lower maximum fan speed will typically generate less fan noise. In an alternative embodiment, a maximum fan speed is set for one or more cooling fans based upon a delta from one or more other commanded fan speeds. For instance, if a delta is set of 15% for a first cooling fan  24  over a fan speed of a second cooling fan  24  that has a setting of 50%, then the maximum fan speed of the first cooling is 65%. The second cooling fan used for the base onto which the delta is added may be selected with a number of criteria, such as the lowest commanded fan speed of all of cooling fans  24 , the median commanded fan speeds of all cooling fans  24 , the mean commanded fan speeds of all cooling fans  24 , or the commanded fan speed of one or more proximately located cooling fans  24 . Restricting fan speeds based upon a delta over other commanded fans speeds effectively takes into account the overall thermal state within chassis  12  so that hot spots within a chassis  12  do not result in inordinate cooling fan power consumption to the detriment of processing operations. 
         [0023]    Referring not to  FIG. 3 , a flow diagram depicts a process for setting cooling fan speeds based upon available chassis power resources. The process starts at step  42  with setting of an initial fan speed configuration that allows commands for fan speeds up to the available fans speeds of all cooling fans. In alternative embodiments, the initial fan speed configuration may include some restrictions on some or all cooling fan speeds below maximum available fan speeds, such as to restrict acoustics. At step  44 , fan speeds are set with the fan speed configuration based upon sensed thermal conditions. At step  46 , a determination is made of whether power consumed at the information handling system exceeds a threshold. If not, the process returns to step  44  to continue to set cooling fan speeds according to the first fan speed configuration. If the power consumption threshold is met at step  46 , the process continues to step  48  to set a second fan speed configuration associated with reduced available power. At step  50  cooling fan speeds are set according to the reduced power state fan speed configuration. For example, a cap is placed on cooling fan speeds to not exceed a delta over the lowest commanded cooling fan speed. At step  52  a determination is made of whether the power consumption threshold remains met. If the power consumption threshold remains, the process returns to step  50  to set cooling fan speeds according to the second fan speed configuration. If the power consumption threshold is no longer met, the process returns to step  42  to set the initial fan speed configuration. 
         [0024]    Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.