The Green Grid 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.
1 A B C D E F G H I K L M N O P R S T U V W Z

A file that contains a sequence of instructions for an interpreter or the script for that interpreter to follow


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)


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, Air- and Liquid-cooled

Server that requires both air and liquid provided by the building

Server, Air_cooled

An air-cooled server that accepts only room air

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


Known as SPEC SFS, SFS93 is the NFS server benchmark which evolved from LADDIS


SPEC SFS97 is the NFS server benchmark which replaced SFS93


SFS97_R1 is version 3 of the NFS benchmark, replacing the SFS97 suite


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


Sensible heat ratio

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)

Single Precision

A level of floating point accuracy that usually requires half the space for each value than does double precision, but provides considerably less precision. For most systems running the SPEC CPU tests from the OSG (e.g., CPU95), single precision implies a 32-bit value

Single-point Failure

Any component that has the capability of causing failure of a system or a portion of a system if it becomes inoperable


Service level agreement


Single-mode fiber


Signal-to-noise ratio

Sound Transmission Class (STC)

This is an acoustical rating for the reduction in sound of an assembly. It is typically used to denote the sound attenuation properties of building elements, such as walls, floors, and ceilings. The higher the STC, the better the sound-reducing performance of the element

Source Code

The human readable form of a computer program. This is typically the form in which the program is written, read, and modified by its human author(s)


A common (mis)name for the CPU95 benchmarks. Also, SPEC89 implies CPU89, SPEC92 should be CPU92, and SPEC2000 is CPU2000


Official name of the Gamess application of SPEChpc96, an application representative of computations used by the chemical industry


The first benchmark suite released by SPEC/HPG, and it includes the two applications Seismic and Gamess


SPECjvm98 is the current Java Virtual Machine benchmark suite from SPEC


SPECmarks were the metrics for SPEC's original CPU89 benchmarks. Now, the term is often used to refer collectively to the CPU95 ratio speed metrics


A throughput metric based on the SPEC CPU benchmarks, such as SPEC CPU95. This metric measures a system's capacity for processing jobs of a specified type in a given amount of time. The metric is used the same for multi-processor systems and for uniprocessors. It is not necessarily a measure of how fast a processor might be, but rather a measure of how much work the one or more processors can accomplish. SPECrates are one style of metric from the SPEC CPU benchmarks, the other are SPECratios


A measure of how fast a given system might be. It is calculated by taking the elapsed time that was measured for a system to complete a specified job and dividing that into the reference time (the elapsed time that job took on a standardized reference machine). This measures how quickly, or more specifically, how many times faster than a particular reference machine, one system can perform a specified task. SPECratios are one style of metric from the SPEC CPU benchmarks, the other are SPECrates


Official name of the Seismic application of SPEChpc96. It is an application representative of computations used by the seismic industry


SPECweb2005 is a standardized performance test for WWW servers, the successor to SPECweb99 and SPECweb99_SSL. The benchmark consists of different workloads (both SSL and non-SSL), such as banking and e-commerce, and writes dynamic content in scripting languages to more closely model real-world deployments. The web server also communicates with a lightweight backend to simulate an application/database server


SPECweb96 is SPEC's first attempt at a benchmark for WWW servers. It measures a server's ability to handle HTTP/1.0 GET requests from a number of external client drivers


SPECweb99 is one of the current web server benchmarks, which replaced the SPECweb96 product


For the OSG, the entity that has accepted the license agreement. In other words, the people who are responsible for ensuring that the results were obtained in accordance with any existing run and reporting rules. For the HPG, See benchmark sponsor who is a technical advisor for a particular benchmark

Standard Performance Evaluation Corporation (SPEC)

An organization of computer industry vendors dedicated to developing standardized benchmarks and publishing reviewed results

Static RAM (SRAM)

Random access memory (RAM) that retains data bits in its memory as long as power is being supplied. SRAM provides faster access to data and is typically used for a computer's cache memory

Static UPS

See UPS, static

Steering Committee

Part of the SPEC bureaucracy. Each free-standing group within SPEC has a steering committee that acts as the key decision-making body with full membership votes typically being reserved for benchmark ratifications and elections

Supply Air

See air, supply


A layer 2 interconnection device that conforms to the ISO/IEC 10038 [ANSI/IEEE 802.1D-1998]


Combination of electrical disconnects and/or circuit breakers meant to isolate equipment in or near an electrical substation

Symbol Rate (SR)

Within IEEE 802.3, the total number of symbols per second transferred to or from the medium dependent interface (MDI) on a single wire pair. For 100BASE-T4, the symbol rate is 25 MBd. For 100BASE-X, the symbol rate is 125 MBd. For 100BASE-T2, the symbol rate is 25 MBd. For 1000BASE-T, the symbol rate is 125 MBd

System Under Test (SUT)

The system being tested, as distinct from anything in the testbed being used to drive the test

System, Air Cooled

Conditioned air is supplied to the inlets of the rack/cabinet for convective cooling of the heat rejected by the components of the electronic equipment within the rack. It is understood that within the rack, the transport of heat from the actual source component (e.g., CPU) within the rack itself can be either liquid- or air-based, but the heat rejection media from the rack to the terminal cooling device outside of the rack is air