System and method for managing information handling system power supply capacity utilization based on load sharing power loss

An information handling system having plural processing modules, such as an information handling system blade chassis having plural information handling system blades, allocates power by determining an actual load sharing power loss associated with plural power supplies and applying the actual load sharing power loss to determine how much power to allocate to the information handling system modules. A chassis manager determines actual load sharing power loss by retrieving power information from plural power supplies. The actual load sharing power loss replaces a worst-case load sharing power loss assumed value to increase the amount power available for allocation to the information handling system modules.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to the field of information handling system power supply, and more particularly to a system and method for managing information handling system power supply capacity utilization.

2. Description of the Related Art

As information handling systems have grown more powerful over time, the infrastructure that supports operation of the information handling systems have had to adapt to increased power consumption. For example, central processor units (CPUs) that perform greater numbers of calculations per time unit typically consume more power than less-powerful counterparts. In addition to the power consumption increase tied to the greater number of calculations, more powerful CPUs also typically produce greater amounts of heat as a byproduct of their operation. The increased thermal energy generally calls for the use of more powerful cooling fans to keep the information handling system within a desired operating range. One approach to address greater infrastructure needs is to support multiple information handling systems within a common chassis that has shared infrastructure. For example, blade servers typically support multiple blades in a common chassis with the blades sharing cooling and power resources under the management of a chassis management controller (CMC). Efficiencies often result when infrastructure is shared, especially where a single hardware device supports multiple information handling systems so that fewer hardware devices are needed and overall cost is reduced. For example, a blade chassis might have three power supplies shared between a dozen blades using a power budget managed by the CMC.

One difficulty that arises when multiple power supplies are used in a system is that some available power is lost when the power load is shared across multiple power supplies. The actual power available to the system is the sum of the power supplied by the individual power supplies corrected for system factors, such as efficiency and system overhead, minus the power lost to the load sharing mechanism, known as the load sharing power loss. In order to prevent any one power supply from exceeding its capacity, information handling systems typically assume a worst case load sharing power loss based on the actual power supplies when setting the system's power budget. For example, a worst case load sharing power loss might reflect extremes of the possible power distribution that covers 99.5% of the entire population of available power supplies. Thus, in actual systems, the actual load sharing power loss is designed to be much lower than the worst case numbers that are assumed to create the power budget. However, using worst case assumptions to generate a power budget typically means that some of the available capacity of the power supplies goes unused. Where the available power supply capacity is close to the expected demand of information handling systems that use the power, the system is typically loaded with more expensive power supplies that have greater capacity or operated with less expensive power supplies at reduced levels that consume less power.

SUMMARY OF THE INVENTION

Therefore a need has arisen for a system and method which measures actual load sharing power loss associated with multiple power supplies for improved power supply capacity utilization.

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 managing power supply capacity utilization. Actual load sharing power loss associated with plural power supplies is determined and applied to allocate power to one or more information handling systems. The use of actual load sharing power loss releases excess power otherwise claimed by worst case load sharing power assumptions so that a greater portion of available power capacity is used to power the one or more information handling systems.

More specifically, an information handling system blade chassis supports plural information handling system blade processing modules with power supplied from plural power supplies under the management of a chassis manager. A power manager running on the chassis manager retrieves power information from the power supplies through a power management bus to compute an actual load sharing power loss associated with the plural power supplies. The actual load sharing power loss is used to determine the amount of power available for allocation to the information handling systems, such as by replacing an initial load sharing power loss assumption value with the actual value. Power output as a measured percentage of load for the power supplies is determined by retrieving power out values from each power supply and averaging the power out values. Actual load sharing power loss is computed by summing the difference of the largest power out value from the remaining power out values as provided by the power supplies.

The present invention provides a number of important technical advantages. One example of an important technical advantage is that measuring actual load sharing power loss with plural power supplies in a modular chassis allows a chassis management controller to assign a greater amount of power to modular information handling systems. Additional power is available from the power supplies because actual measurement of power load sharing loss reduces the amount of power set aside in a worst case power load sharing scenario. The additional power provided from measuring actual load sharing power loss helps to reduce the cost of information handling systems supported in a modular chassis by working will smaller and less expensive power supplies and also helps to ensure that information handling systems operate at full capacity or closer to full capacity than is possible with worst case load sharing power loss assumptions. For example, in one embodiment having three power supplies, the use of actual load sharing power loss provides 400 Watts of power over a worst case power loss assumption.

DETAILED DESCRIPTION

Referring now toFIG. 1, a block diagram depicts a system for allocation of power using actual load sharing power loss. An information handling system blade chassis10supports plural information handling system blade processing modules12in plural blades slots14. Information handling system blade processing modules12are built with plural processing components that cooperate to process information, such as a CPU16, RAM18, hard disk drive20, network interface card22and chipset24. A baseboard management controller26provides out of band management of each processing module12, such as with a chassis manager28that communicates over a management bus30. Processing modules12receive power from plural power supplies32through a chassis power rail34under the management of chassis manager28. The use of multiple power supplies32introduces a load sharing power loss so that the total power available from the multiple power supplies32is less than the total power available from the sum of each power supply operating individually. Chassis manager28includes logic that retrieves power information from power supplies32through a power management bus36and applies the power information to determine an actual load sharing power loss. The actual load sharing power loss replaces a default load sharing power loss value so that chassis manager28has the difference between the actual and default values for use by processing modules12. AlthoughFIG. 1depicts a system for applying actual load sharing power loss for power management at a blade chassis10having plural blade processing modules12, in alternative embodiments alternative types of information handling systems operating individually or in common with plural power supplies may use the power management described herein.

Referring now toFIG. 2, a block diagram depicts a system for allocation of power using actual load sharing power loss. An end user interacts with the system through a Remote Access Controller Administration (RACADM)38, such as a Remote Access Controller administration interface firmware module running on chassis manager28, or Web graphical user interface40to set an AC power limit in Watts that represents available external power. A power manager42, such as a firmware module running on chassis manager28, translates the AC power limit to create a DC power budget based on a number of factors, such as the number of power supplies present, the number of power supplies that are online and operational, a measurement of the actual load sharing power loss and the power allocated to infrastructure, such as power that runs chassis cooling and management subsystems. Power manager42retrieves power information from power supplies32through a power supply power management bus layer44, a hardware extraction layer46an12C bus driver48and a power supply bus microcontroller50that manages communication between chassis manager28and power supplies32. For example, power manager42performs enumeration of power supplies32to count available and operating power supplies and their efficiencies which are published through power management bus36. Power manager42determines percentage load condition ranges to compute DC power translated from available AC power. Power manager42measures actual load sharing power loss by profiling power out measurements retrieved from power supplies32against a percentage of load ranges, such as with an average computed from multiple repeated power out measurements. The profile of power out measurements is analyzed to determine an actual load sharing power loss over a range of power out values. Power manager42then replaces a default load sharing power loss value used to initiate the system with the actual load sharing power loss to determine the amount of power that is available for allocation to information handling system10.

Referring now toFIG. 3, a flow diagram depicts a process for power allocation with actual load sharing power loss. The process begins at step52with an AC power limit input by an end user, such as through a Web GUI or a remote interface. The process continues to step54for discovery from the power supply units of power information to compute available DC power based on the AC power limit and the power supply information. For example, an enumeration of the power supplies and factors in a power supply count that includes power supply efficiency provides percentage of load condition ranges to compute DC power translated from AC power. DC power available to processing modules depends upon the number of operating power supplies, their efficiency, administrative overhead and load sharing power loss, which is initially set at a default value. The process continues to step56to measure output power from the power supplies. A power management bus (PMBus) interface provides measurements made at each power supply for output power in Watts in response to a POUT command. At step58, a profile table is created for POUT measurements against a percentage of load ranges. POUT readings are retrieved from each power supply in back to back power management bus transactions and repeated over n samples in rapid succession to compute an averaged POUT measurement. Power out readings taken in rapid succession at a firmware level, such as in hardware abstraction layer46, minimize latency to provide a more accurate measure of power out.FIG. 4depicts a block diagram of an example of a process flow of information between power supplies32and chassis manager28to create a power output table64. For a given measured percentage of load, the actual load sharing power loss is computed by taking a sum of the differences between the greatest power out value and each other power out value, as depicted inFIG. 4by formula66.

Returning toFIG. 3, at step60an actual load sharing power loss is determined based on the power out measurements. Load share loss between a pair of power supplies is constant from 20% to 100% of load so that any measurement while the power supplies are over 20% of load provides useful data. Formula66fromFIG. 4depicts on example of a computation of load sharing power loss. Use of formula66provides an actual measurement of load sharing power loss in a given power supply configuration. Load sharing power loss is computed by collecting power out readings from all power supplies for percentage of load condition samples and determining the difference from the highest reading between all other measure readings. At step62, power allocation to the information handling system is managed with the actual load sharing power loss value in the place of any estimated load sharing power loss value, such as a default worst case value used to initialize the system. This enables allocation of additional power for use by the information handling system that was otherwise tied up in worst case load sharing power loss assumptions.FIG. 5depicts an example of estimated load sharing power loss that is reclaimed as the number of power supplies is decreased, such as with a power supply failure. Excess load sharing power that is available as power supplies drop off line is used to increase power available for running the information handling system.