The maximum load during a specified period of time. On a daily basis, peak loads occur at midmorning and in the early evening. Source: United States Energy Information Administration
TGG Glossary
This is a glossary of older terms. While many of the definitions are unchanged, some of the definitions may be out of date and some of the terms may no longer be in use in the Data Center industry. This legacy glossary provides definitions for hundreds of information and communications technology (ICT) and data center terms and acronyms. Arranged alphabetically and searchable, the glossary explains common industry vocabulary.
Peak demand
Perforated Floor Tile
A tile as part of a raised-floor system that is engineered to provide airflow from the cavity underneath the floor to the space. Tiles may be with or without volume dampers
Performance Neutral
Performance neutral means that there is no significant difference in performance. For example, a performance neutral source code change would be one which would not have any significant impact on the performance as measured by the benchmark
Personal Digital Assistant (PDA)
A hand-held computer or personal organizer device
PFCs
Numerous perfluorocarbons, an EPA targeted greenhouse chemical. Source: United States Environmental Protection Agency
PFLOPs
petaFLOPS. A measure of computer performance equal to 1015 floating point operations per second. Source: ASHRAE
Physical Layer Entity (PHY)
Within IEEE 802.3, the portion of the physical layer between the medium mependent interface (MDI) and the media independent interface (MII), gigabit media independent interface (GMII), or 10 gigabit media independent interface (XGMII) consisting of the physical coding sublayer (PCS), the physical medium attachment (PMA), and if present, the WAN interface sublayer (WIS) and physical medium dependent (PMD) sublayers. The PHY contains the functions that transmit, receive, and manage the encoded signals that are impressed on and recovered from the physical medium (for example, see IEEE 802.3, Clauses 23-26, Clause 32, Clause 36, Clause 40, Clauses 48-54, Clauses 58-63, Clause 65, and Clause 66)
Pictogram
A graphical composition that may include a symbol plus other graphical elements, such as a border, background pattern or colour that is intended to convey specific information. Source: United Nations GHS
Plenum
A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system (NFPA definition)
Point of Presence (PoP)
A place where communication services are available to subscribers. Internet service providers have one or more PoPs within their service area that local users dial into. This may be co-located at a carrier's central office
Pool Boiling
A classification type of data center cooling for high heat density liquid cooling of data center equipment. Uses direct liquid cooling through immersion or spray. Source: NVIDIA
Portability
Portability flags or changes are those which are necessary for the correct execution of a benchmark. That is, the benchmark will not run or will produce the wrong output without these flags or changes
Portable
In computer terms, portable means that the code in question can be easily taken to a different system and made to work there. Code that is dependant upon quirks or specific resources of a certain system is usually considered not to be portable because of the difficulties in finding means of supporting these dependencies on the new system. The use of standardized definitions and interfaces, e.g., ANSI-C and POSIX, greatly aids portability because the difficult dependencies are hidden behind the standardized interfaces and the difficulties are shifted from the programmer to the system provider
Power
Time rate of doing work usually expressed in horsepower or watts
Power Bus (or Electrical Bus)
See bus, power
Power Distribution Unit (PDU)
The junction point between the UPS and the cabinets containing equipment
Power Distribution Unit (PDU)
A device for controlling electrical power in a data center. Source: Tech Target
Power Factor
The ratio of real power (kilowatt) to apparent power kilovolt-ampere for any given load and time. Source: United States Energy Information Administration
Power Supplies
A component type of data center class server. Source: Intel
Power Usage Effectiveness (PUE)
Globally accepted metric that is described by The Green Grid in several whitepapers. PUE illustrates the total energy used by a data center divided by the energy used by ICT equipment in that data center
Printed Circuit Board (PCB)
Board that contains layers of circuitry used for interconnecting the other components
Processor
See central processing unit (CPU)
Procurement & Contracting Personnel
A stakeholder in the decision to invest, divest, use, source liquid cooled data center environments. Source: United States Department of Energy CoE
Product Identifier
The name or number used for hazardous product on a label or in the SDS. It provides a unique means by which the product user can identify the substance or mixture within the particular use setting e.g., transport, consumer, or workplace. Source: United Nations GHS
psi
Pressure per square inch a unit of pressure. Source: ASHRAE
PSU
Power Supply Unit. Source: OCP
Psychrometric Chart
A graph of the properties (temperature, relative humidity, etc.) of air. It is used to determine how these properties vary as the amount of moisture (water vapor) in the air changes
PUE
Power usage effectiveness. A metric used to describe facility efficiency defined simply as the energy entering the facility divided by the energy used by the IT equipment. A facility with equal amounts of overhead and IT energy would have a PUE of 2.0 because only half of the energy is used to power the IT equipment. Overhead can be attributed to many things such as cooling, power conversion, lighting, office equipment not performing the functions of the IT equipment, etc. A partial PUE would an example of a breakdown of the overhead into a specific function such as the cooling partial PUE consisting of all energy associated with the cooling function. Source: ASHRAE
Pump
Machine for imparting energy to a fluid, causing it to do work
* Centrifugal pump: Pump having a stationary element (casing) and a rotary element (impeller) fitted with vanes or blades arranged in a circular pattern around an inlet opening at the center. The casing surrounds the impeller and usually has the form of a scroll or volute
* Diaphragm pump: Type of pump in which water is drawn in and forced out of one or more chambers by a flexible diaphragm. Check valves let water into and out of each chamber
* Positive displacement pump: Has an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. Examples of positive displacement pumps include reciprocating pumps and rotary pumps
* Reciprocating pump: A back-and-forth motion of pistons inside of cylinders provides the flow of fluid. Reciprocating pumps, like rotary pumps, operate on the positive principle. That is each stroke delivers a definite volume of liquid to the system
* Rotary pump: Pumps that deliver a constant volume of liquid regardless of the pressure they encounter. A constant volume is pumped with each rotation of the shaft and this type of pump is frequently used as a priming pump
QSFP
Quad (4-channel) Small form factor Pluggable: a common optical component type for data center servers and other computing and communications equipment. Source: OCP
Rack (from ASHRAE, industry)
Structure for housing electronic equipment. Differing definitions exist between the computing industry and the telecommunications industry
* Computing industry: A rack is an enclosed cabinet housing computer equipment. The front and back panels may be solid, perforated, or open depending on the cooling requirements of the equipment within
* Telecommunications industry: A rack is a framework consisting of two vertical posts mounted to the floor and a series of open shelves upon which electronic equipment is placed. Typically, there are no enclosed panels on any side of the rack
Rack (from ASHRAE)
Frame for housing electronic equipment
Rack Power
Used to denote the total amount of electrical power being delivered to electronic equipment within a given rack. Often expressed in kilowatts (kW), this is often incorrectly equated to be the heat dissipation from the electrical components of the rack
Rack-mounted Equipment
Equipment that is to be mounted in an EIA (Electronic Industry Alliance) or similar cabinet. These systems are generally specified in EIA units, such as 1U, 2U, 3U, etc., where 1U = 1.75 inches (44 mm)
Rack, Air- and Liquid-cooled
Rack that requires both air and liquid provided by the building
Rack, Air-cooled
System conditioned by removal of heat only using air
Rack, Liquid-cooled
A liquid-cooled rack that accepts conditioned coolant; system conditioned by removal of heat using a liquid
RAID Controllers
A component type of data center class server. Source: Intel
Raised Floor (from ASHRAE, industry)
Also known as access floor. Raised floors are a building system that utilizes pedestals and floor panels to create a cavity between the building floor slab and the finished floor where equipment and furnishings are located. The cavity can be used as an air distribution plenum to provide conditioned air throughout the raised floor area. The cavity can also be used for routing of power/data cabling infrastructure
Raised Floor (from ASHRAE)
A platform with removable panels where equipment is installed with the intervening space between it and the main building floor used to house the interconnecting cables, which at times is used as a means for supplying conditioned air to the information technology equipment and the room
Random Access Memory (RAM)
A configuration of memory cells that hold data for processing by a computer's processor. The term random derives from the fact that the processor can retrieve data from any individual location, or address, within RAM
Rated Current
The rated current is the absolute maximum current that is required by the unit from an electrical branch circuit
Rated Frequency
The supply frequency as declared by the manufacturer
Rated Frequency Range
The supply frequency range as declared by the manufacturer expressed by its lower and upper rated frequencies
Rated Voltage
The supply voltage as declared by the manufacturer
Rated Voltage Range
The supply voltage range as declared by the manufacturer
RC-class
Room-cooling class
RDHX
Rear door heat exchanger, a classification type of data center cooling for high heat density air cooling. Source: NVIDIA
RDIMM
Registered memory DIMM. Source: ASHRAE
Rear Door Heat Exchanger (RDHx)
A specialized IT Cabinet rear door with a built-in heat exchanger that uses a radiator where the hottest servers are operating. chills the hot air from the back of the servers and cools it immediately. The chilled door contains fans and a coolant. The coolant absorbs the heat, returning cooler air to the data center. Source: Supermicro
Redfish
Standard designed to deliver simple and secure management for converged, hybrid IT and the Software Defined Data Center (SDDC). Both human readable and machine capable, Redfish leverages common Internet and web services standards to expose information directly to the modern tool chain. Source: DMTF
Redundancy (from ASHRAE)
"N" represents the number of pieces to satisfy the normal conditions. Redundancy is often expressed compared to the baseline of "N." Some examples are "N+1," "N+2," "2N," and 2(N+1). A critical decision is whether "N" should represent just normal conditions or whether "N" includes full capacity during off-line routine maintenance. Facility redundancy can apply to an entire site (backup site), systems, or components. IT redundancy can apply to hardware and software
Reference Time
The amount of time that a particular benchmark took to run on a specific reference platform
Refrigerants
In a refrigerating system, the medium of heat transfer that picks up heat by evaporating at a low temperature and pressure and gives up heat on condensing at a higher temperature and pressure
Relative Humidity (RH)
* Ratio of the partial pressure or density of water vapor to the saturation pressure or density, respectively, at the same dry-bulb temperature and barometric pressure of the ambient air
* Ratio of the mole fraction of water vapor to the mole fraction of water vapor saturated at the same temperature and barometric pressure at 100% relative humidity, the dry-bulb, wet-bulb, and dew-point temperatures are equal
Releasing Panel
A particular fire alarm control panel whose specific purpose is to monitor fire detection devices in a given area protected by a suppression system and, upon receiving alarm signals from those devices, actuate the suppression system
Reliability
The degree to which the result of a measurement, calculation, or specification can be depended on to be accurate. Source: Oxford Languages
Reliability (from ASHRAE, industry)
Reliability is a percentage value representing the probability that a piece of equipment or system will be operable throughout its mission duration. Values of 99.9 percent (three 9s) and higher are common in data and communications equipment areas. For individual components, the reliability is often determined through testing. For assemblies and systems, reliability is often the result of a mathematical evaluation based on the reliability of individual components and any redundancy or diversity that may be employed
Reliability (from ASHRAE)
A percentage value representing the probability that a piece of equipment or system will be operable throughout its mission duration. Values of 99.9% (three 9s) and higher are common in data and communications equipment areas. For individual components, the reliability is often determined through testing. For assemblies and systems, reliability is often the result of a mathematical evaluation based on the reliability of individual components and any redundancy or diversity that may be employed
Remote Power Panel (RPP)
A term typically used to describe electrical panels outside of electrical equipment rooms
Reporting Rules
The set of benchmark rules that defines what constitutes a valid full disclosure for that benchmark. Usually these define what parts of the benchmark configuration and the system configuration(s) that need to be detailed and disclosed
Response Time
The amount of time from when an action is requested until the time that the request completes and is returned to the requestor
Result
The value of the primary metric being reported for the benchmark
Return Air (RA)
See air, return
RHI
Return Heat Index
RISE
Responsible, inclusive, and sustainable world, enabled (through technology). Source: Intel
Riser
A vertical pipe in a building
Risk
The potential for adverse consequences where something of value is at stake and where the occurrence and degree of an outcome is uncertain. In the context of the assessment of climate impacts, the term risk is often used to refer to the potential for adverse consequences of a climate-related hazard, or of adaptation or mitigation responses to such a hazard, on lives, livelihoods, health and well-being, ecosystems and species, economic, social, and cultural assets, services (including ecosystem services), and infrastructure. Risk results from the interaction of vulnerability (of the affected system), its exposure over time (to the hazard), as well as the (climate-related) hazard and the likelihood of its occurrence. Source: IPCC
Room Load Capacity
The point at which the equipment heat load in the room no longer allows the equipment to run within the specified temperature requirements of the equipment. The load capacity is influenced by many factors. The primary one is the room's theoretical capacity. Other factors, such as the layout of the room and load distribution, also influence the room load capacity
Room Theoretical Capacity
The capacity of the room based on the mechanical room equipment capacity. This is the sensible tonnage of the mechanical room for supporting the computer or telecommunications room heat loads
Rotary Heat Exchanger
See exchanger, rotary heat
Rotary UPS
See UPS, rotary
Router
A layer 3 interconnection device that appears as a media access control (MAC) to a CSMA/CD collision domain (see IEEE Std 610.7-1995 [B38])
Run Rules
The set of benchmark rules that defines what constitutes a valid test with that benchmark. Usually these define legal configurations, experimental limitations, and any operating constraints
Safety Data Sheet
A formatted document containing comprehensive information about a substance or mixture for use in workplace chemical control regulatory frameworks by employers and workers. Target audiences include transporters, emergency responders (including poison centers) and consumers. Typically printed and found in immediate adjacency to the substance or mixture to promote workplace safety. See Appendix XX the Safety Data Sheet format for the United States. Formerly known as Material safety data sheet. Source: United Nations GHS
SCHX
Script
A file that contains a sequence of instructions for an interpreter or the script for that interpreter to follow
SDRAM
Synchronous dynamic random-access memory. Source: ASHRAE
SDS
Safety Data Sheet. Source: United Nations GHS
SEC
United States Securities and Exchange Commission. Source: PwC
Second(s)
The SI unit of time. It is defined by taking the fixed numerical value of the cesium frequency ΔνCs, the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s-1. Source: BIPM
Semiconductor
A material that is neither a good conductor of electricity nor a good insulator. The most common semiconductor materials are silicon, gallium arsenide, and germanium. These materials are then doped to create an excess or lack of electrons and used to build computer chips
Sensible Heat Load
See heat load, sensible
Sensible Heat Ratio (SHR)
Ratio of the sensible heat load to the total heat load (sensible plus latent)
Server
A computer that provides some service for other computers connected to it via a network. The most common example is a file server, which has a local disk and services requests from remote clients to read and write files on that disk
Server
An item specifically designed to function as a node on a computer network and provides service to terminals on the network through managing an expansive shared resource. Includes file server which manages a set of disks and provide storage and archival services to computers on the network that may or may not have their own disks, printer server which provides high quality and/or high-speed printing so that each terminal on the network need not have its own printer, and/or communications server which provides connection to various communication media including other LANs and/or public networks. Excludes: PROCESSOR, FILE SERVER. [ FIIG=A23900;INC=53149 || DLIS || ISO 22745-11 Source: eOTD ECCMA Open Technical Dictionary is an ISO 22745 compliant dictionary managed by ECCMA
Server, Air_cooled
An air-cooled server that accepts only room air
Server, Air- and Liquid-cooled
Server that requires both air and liquid provided by the building
Server, Liquid-cooled
A liquid-cooled server that accepts conditioned coolant
Service Level Agreement (SLA)
A contract between a network service provider and a customer that specifies, usually in measurable terms, what services the network service provider will furnish
SF6
Sulfur hexafluoride, an EPA targeted greenhouse gas. Source: Unites States Environmental Protection Agency
SFS93
Known as SPEC SFS, SFS93 is the NFS server benchmark which evolved from LADDIS
SFS97
SPEC SFS97 is the NFS server benchmark which replaced SFS93
SFS97_R1
SFS97_R1 is version 3 of the NFS benchmark, replacing the SFS97 suite
Shell
A UNIX term for a command interpreter and its environment. Typically a program that supports the interpretation and execution of commands
Shielded Twisted-pair (STP) Cable
An electrically conducting cable, comprising one or more elements, each of which is individually shielded. There may be an overall shield, in which case the cable is referred to as shielded twisted-pair cable with an overall shield (from ISO/IEC 11801: 1995). Specifically for IEEE 802.3 100BASE-TX, 150 O balanced inside cable with performance characteristics specified to 100 MHz (i.e., performance to Class D link standards as per ISO/IEC 11801: 1995). In addition to the requirements specified in ISO/IEC 11801: 1995, IEEE Std 802.3, Clause 23 and Clause 25, provide additional performance requirements for 100BASE-T operation over STP
SHR
Sensible heat ratio
SI
Système international d’unités/International System of Units. Source: BIPM
Signal Word
A word used to indicate the relative level of severity of hazard and alert the reader to a potential hazard on the label. The GHS uses "Danger" and "Warning" as signal words. Source: United Nations GHS
Simplex Fiber Optic Link Segment
A single fiber path between two medium attachment units (MAUs) or PHYs, including the terminating connectors, consisting of one or more fibers joined serially with appropriate connection devices, i.e., patch cables and wall plates (see IEEE 802.3, Clause 15)