Glossary

Datacenter Technical Terms

2N Power

An electrical architecture in which every piece of equipment has two independent power feeds, each capable of supporting the full load on its own. If one source fails, the other takes over instantly with no interruption. This is the standard for Tier III and Tier IV datacenters.

Rack (cabinet)

A standardized metal enclosure that houses servers and IT equipment. Its capacity is measured in U (rack units). At NEXEREN, our high-density racks accommodate high-power-consumption equipment, particularly AI and GPU infrastructure.

Private cage

A partitioned, secured space within a datacenter reserved for the exclusive use of a single client. Unlike a rack in a shared space, a private cage provides total physical isolation: restricted access, zero visibility from other areas — ideal for sensitive or large-scale infrastructure.

Availability / SLA

Availability expresses the percentage of time an infrastructure is operational over a year. An SLA (Service Level Agreement) is the contractual commitment to that rate. A 99.98% SLA corresponds to less than 1 hour 45 minutes of downtime per year. At Nexeren, CV1 guarantees a 99.98% SLA.

Backup generator

A diesel- or gas-powered backup generator that takes over in the event of a public power grid outage. In a datacenter, it ensures continuity of power beyond the runtime.

High power density

Describes a rack or space capable of accommodating equipment with very high power consumption, typically above 10 kW per rack. AI infrastructure (GPU servers) requires high-density racks. Nexeren offers high-density racks across its entire network.

PUE (Power Usage Effectiveness)

An indicator of a datacenter’s energy efficiency. It is calculated by dividing the total power consumed by the site by the power actually used by the IT equipment. A PUE of 1.0 is the theoretical maximum (all energy goes to the equipment). Below 1.3, a datacenter is considered highly efficient. Nexeren maintains a PUE below 1.3 across all its sites, with a minimum of 1.13 at CBZ.

Redundancy

The principle of duplicating equipment or critical paths (power, cooling, network) so that a failure in one component does not cause a service interruption. The higher the level of redundancy, the greater the guaranteed availability.

Precision cooling

An air conditioning system specifically designed for IT rooms, maintaining stable temperature and humidity regardless of outside conditions. More precise and reliable than standard air conditioning, it protects equipment from thermal fluctuations.

U (rack unit)

A unit of measurement for the height of equipment in a rack. 1U = 44.45 mm. A standard server typically takes up 1U to 2U; a high-density GPU server can take up 4U to 8U.

UPS (Uninterruptible Power Supply)

A system that maintains power during brief outages or micro-interruptions, or for the time it takes the backup generator to kick in. It protects equipment against voltage fluctuations and short power cuts. Connectivity

Patching

The physical operation of connecting or disconnecting network or fiber-optic cables on a patch panel. In a datacenter, patching is carried out by technicians during cabling or network reconfiguration work.

Carrier-neutral

A carrier-neutral datacenter does not impose any exclusive telecom operator. Clients are free to choose their connectivity providers from among those present on site. Nexeren is carrier-neutral across all of its datacenters.

Dark fiber

Optical fiber provided without any intermediate active equipment. The client has access to raw fiber and deploys their own transmission equipment on it (transponders, DWDM, etc.). This offers maximum freedom and capacity, at the cost of greater technical management.

Interconnection

A physical or logical link connecting two sites, two networks, or two operators. Nexeren interconnects all of its datacenters with one another and has an extensive network reaching many other sites across France.

LAN to LAN

A Layer 2 (data link layer) interconnection service that links multiple sites as if they belonged to the same local network. Your equipment communicates seamlessly from one site to another, with no intermediate routing.

IP transit

A service that lets your hosted equipment access the entire internet via an operator’s network. Nexeren offers high-performance, redundant IP transit internet access from its datacenters.

Wave (wavelength)

A dedicated optical transport service using a specific wavelength on a shared fiber. Unlike dark fiber, a wave service includes the active transmission equipment. It offers guaranteed throughput of up to several hundred Gbit/s, with controlled latency and protocol transparency. Certifications & Compliance

CLOUD Act

A 2018 U.S. law (Clarifying Lawful Overseas Use of Data Act) that allows U.S. authorities to compel a company subject to U.S. law to disclose data stored abroad. Datacenters operated by providers subject to U.S. law — even if physically hosted in Europe — can be affected. Nexeren, a French operator, is not subject to the CLOUD Act.

FISA

A U.S. surveillance law (Foreign Intelligence Surveillance Act) that allows U.S. intelligence agencies to access the communications and data of foreign nationals passing through infrastructure operated by companies subject to U.S. law. A key argument in favor of sovereign hosting with a French operator.

HDS (Health Data Hosting certification)

A mandatory French certification for any organization hosting personal health data. It is issued by an accredited body and attests to compliance with a strict security framework, in line with the French Public Health Code. All of Nexeren’s operational sites are HDS-certified.

ISO 27001

The leading international standard for information security management. It covers the confidentiality, integrity, and availability of data handled by the certified organization. All of Nexeren’s operational sites are ISO 27001-certified.

GDPR

The General Data Protection Regulation (GDPR) is the European framework governing the collection, processing, and storage of personal data. It applies to any organization processing the data of European residents, regardless of its location.

Tier I / II / III / IV

A datacenter classification system defined by the Uptime Institute, rating their level of availability and resilience. Tier I: basic infrastructure, 99.671% availability. Tier II: redundant components, 99.741%. Tier III: concurrent maintenance possible without interruption, 99.982%. Tier IV: full fault tolerance, no single point of failure, 99.995%. Certifications exist at two levels: Design (validated design) and Facility (actually built and compliant installation). Nexeren operates sites certified Tier III and Tier IV, both Design & Facility. Sovereignty & Hosting

Colocation

Hosting your own servers and equipment in a professional datacenter. You remain the owner and manager of your hardware; the datacenter provides the hosting environment: power, cooling, physical security, and connectivity.

Hyperscaler

A term referring to the giants of the global cloud (AWS, Microsoft Azure, Google Cloud, etc.) that operate very large-scale datacenters. Their infrastructure is high-performing but subject to extraterritorial legislation (CLOUD Act, FISA), and they offer proprietary cloud services that create technological dependency.

Neutrality (neutral datacenter)

A neutral datacenter does not sell any service that competes with those of its clients and does not impose any exclusive operator. Nexeren is neutral: your hosting provider is never in competition with you.

Smart hands

Physical interventions carried out by datacenter technicians on your equipment, at your request: reboots, cabling, component replacement, inventory checks. This lets you manage your infrastructure remotely without an on-site visit.

Digital sovereignty

An organization’s ability to control its digital infrastructure independently of foreign actors or legislation. In the datacenter context, it means hosting on sites operated by a provider subject exclusively to French and European law.