Glossary¶

General Terms¶

Colocation

A service that allows a customer to place their own server equipment in a professional data center. The customer owns the hardware, while the service provider offers the physical infrastructure — space, power, cooling, connectivity, and security.

Data Center

A specialized building designed for housing and maintaining server equipment. It features constant temperature and humidity, redundant power, fire detection systems, physical security, and reliable network connectivity.

Tier Classification

The Uptime Institute standard for rating data center reliability:

Tier I — basic facility, no redundancy (99.671% availability)
Tier II — partial redundancy (99.741% availability)
Tier III — concurrently maintainable (99.982% availability)
Tier IV — fault-tolerant (99.995% availability)

Delta.BG Colocation is provided in a Tier 3+ facility — Tier III with additional reliability measures.

Physical Infrastructure¶

Rack: A metal cabinet with standard dimensions in which server machines are mounted. The most common standard is the 19-inch rack (mounting rail width — 19 inches / 482.6 mm). Rack height is measured in U.
U (Unit): A unit of measurement for equipment height in a rack. 1U = 44.45 mm (1.75 inches). Most standard servers are 1U or 2U in size. A full rack is typically 42U or 48U.
Half-rack: Renting half of a rack — typically 20U–22U. Suitable for medium-sized customers with several machines but who don't need a full rack.
Full-rack: Renting an entire rack with all ~42U. Suitable for customers with many machines or specific isolation requirements.
Rails: Mounting elements installed in the rack that allow the machine to be placed stably. Rails are usually specific to a particular server model and are provided by the manufacturer. They allow the machine to be pulled out of the rack for servicing without full dismantling.
Cold Aisle Containment: A method for optimizing cooling in the data center by physically isolating cold aisles (where servers intake cold air) from hot aisles (where warm air is exhausted). Reduces cold/warm air mixing and increases cooling efficiency.

Power¶

PDU (Power Distribution Unit): A power distribution unit mounted in the rack. Distributes power to the servers installed in the rack. It often has multiple outlets (IEC C13) and can be a "smart PDU" with remote monitoring and control capabilities.
C13 / C14 Connectors: Standard IEC connectors for server equipment power. C13 is a female connector used in PDU outlets in the rack. C14 is the corresponding male connector used by the server power cable. A C14 → C13 cable is the most commonly used to connect a server to a PDU.
UPS (Uninterruptible Power Supply): A device that, during a power outage, continues to power equipment from batteries until diesel generators start or central power is restored.
Dual PSU: A server with two Power Supply Units. Each PSU can power the server independently. When connected to two independent power lines (A and B), the machine continues to operate even if one line fails.
TDP (Thermal Design Power): The maximum thermal power a component (usually CPU) will dissipate under normal load. Used to estimate server power consumption and plan rack cooling.

Networking¶

Peering: A direct connection between two networks for traffic exchange, without an intermediate provider. Peering reduces latency and cost of traffic to common peers.
Internet Exchange (IX): A point where multiple network operators connect to exchange traffic with each other. European IX points such as DE-CIX (Frankfurt), AMS-IX (Amsterdam), and LINX (London) are key for inter-operator connectivity.
Bandwidth: The maximum data transfer rate through the network interface, measured in bits per second (bps). Typical values for colocation: 100 Mbps, 1 Gbps, and 10 Gbps.

Remote Access¶

IPMI (Intelligent Platform Management Interface): A standardized interface for remote server management at a level below the operating system. Allows powering the machine on/off, monitoring hardware metrics, a remote KVM console, and OS installation through a virtually mounted ISO image. Different manufacturers have their own implementations — Dell iDRAC, HPE iLO, Supermicro IPMI, Lenovo XClarity, and others.
BMC (Baseboard Management Controller): A specialized microcontroller on the server motherboard that implements IPMI functionality. The BMC operates independently of the main CPU and OS — even when the machine is powered off, the BMC remains active and provides remote access.
OpenVPN: An open-source VPN protocol for a secure encrypted connection between a client and a network. In the context of colocation, it's used to provide remote access to the IPMI interface without exposing it on the public network.
KVM Console: Keyboard, Video, Mouse — remote access to the server's screen, keyboard, and mouse. An IPMI KVM console allows full control over the machine as if you were sitting in front of the physical server.

Additional Information¶

For more information on how these terms are used in the context of the service, see the relevant sections in the documentation.

If you have questions or need further clarification, please contact our Sales department or our support team.