Glossary
The words of hosting
Twenty-four terms that keep coming up in technical specifications, each defined in two sentences - without needless jargon, and without sending you to another term just as obscure.
- VPS
- A VPS (Virtual Private Server) is a virtual server with its own resources - processor, memory, storage - isolated from those of the other customers on the physical machine. It sits between shared hosting, where everything is shared, and a dedicated server, where the whole machine is yours. Learn more →
- KVM
- KVM (Kernel-based Virtual Machine) is the virtualisation technology built into the Linux kernel. Unlike container-based virtualisation (OpenVZ, LXC), it gives each virtual machine its own kernel and genuinely reserved resources: a neighbour saturating their VPS cannot take yours.
- Hypervisor
- The hypervisor is the software layer that runs several virtual machines on a single physical server and shares the hardware between them. It is what guarantees isolation: what one virtual machine does stays invisible to the others, and without effect on them.
- vCPU
- A vCPU is a virtual processor core allocated to a virtual machine. It corresponds to one execution thread of the physical processor. For most workloads, the clock speed of a vCPU matters more than their number: software that cannot spread across several cores will not run faster on eight vCPUs than on two.
- RAM
- RAM (random access memory) is the server's workspace: everything it is handling at any given moment lives there. Once it is full, the system moves data out to disk (swap) and everything slows down abruptly. It is the first limiting factor for most hosted applications.
- SSD and NVMe
- An SSD stores data on flash memory, with no moving parts, which makes it far faster than a conventional hard drive. NVMe is the protocol that connects the SSD straight to the processor: with identical memory, an NVMe drive answers in microseconds where a SATA SSD takes milliseconds.
- IOPS
- IOPS (Input/Output Operations Per Second) measure how many read or write operations a storage system handles each second. It is the metric that matters for a database, which performs a great many small writes, rather than raw throughput in megabytes.
- Bandwidth
- Bandwidth is the maximum throughput of a network link, expressed in megabits or gigabits per second. It says nothing about latency: a 1 Gbit/s link that is geographically distant is still slow to answer, even though it moves a lot of data once under way.
- Latency (ping)
- Latency is the round-trip time of a packet between client and server, measured in milliseconds. It depends above all on physical distance and on the number of devices crossed. A server in Paris answers in about ten milliseconds from France, against about a hundred from the United States.
- Anti-DDoS
- Anti-DDoS protection filters distributed denial-of-service attacks, which aim to make a server unreachable by drowning it in traffic. Filtering happens upstream of the server, on the network, so that malicious traffic never reaches the machine.
- L3, L4 and L7 attacks
- L3 and L4 attacks saturate the network and transport layers: they try to fill the pipe, and are filtered by volume. L7 attacks target the application itself by imitating genuine visitors, and call for behavioural analysis rather than raw throughput. Serious protection covers both families.
- Dedicated IP
- A dedicated IP is a public address assigned to your server alone, as opposed to an address shared between several customers. It is needed to host a service reachable from outside, to manage your own TLS certificate, or to build a sender reputation for email.
- IPv6
- IPv6 is the current version of the internet addressing protocol, designed to replace IPv4, whose addresses are exhausted. An IPv6 address is written in hexadecimal rather than as four numbers. The two protocols coexist: a modern server generally offers one of each.
- Root SSH access
- The root account is the administrator of a Linux system: it can install, change and delete anything. SSH is the encrypted protocol used to connect to it remotely, on the command line. Having root access means no restriction from the host stands between you and the machine.
- RDP
- RDP (Remote Desktop Protocol) is Microsoft's remote desktop protocol: it displays the Windows Server graphical interface on your own screen. It is the equivalent of SSH for a Windows VPS, except that you work with a mouse rather than on the command line.
- Snapshot
- A snapshot is an instant picture of a server's complete state - disk and configuration - at a given moment. You take one before a risky operation: if the update breaks something, you restore in a few minutes. It is not a backup in the strict sense, because it lives on the same infrastructure.
- Uptime and SLA
- Uptime is the percentage of time during which a service is reachable. The SLA (Service Level Agreement) is the contractual commitment that guarantees it: it sets an availability threshold to be met over the month, and the compensation owed to the customer if that threshold is missed.
- Datacentres and Tier levels
- A datacentre is the building that houses the servers, with its power supply, cooling and security. The Tier classification, from I to IV, measures how redundant those facilities are: a Tier IV site duplicates every critical circuit, which allows maintenance without interrupting service.
- Shared hosting
- Shared hosting places many sites on a single server, with pooled resources and no administrator access. It is the cheapest and simplest option, but a neighbour's load can slow your site down, and you choose neither the software versions nor the configuration. Learn more →
- Dedicated server
- A dedicated server is an entire physical machine reserved for a single customer: no hypervisor, no neighbours, the whole of the processor and the memory. You move to one when the load becomes too heavy or too irregular for a VPS, or when a regulatory constraint requires hardware isolation. Learn more →
- Proxmox VE
- Proxmox VE is an open-source virtualisation platform that lets you create and manage your own KVM virtual machines and LXC containers from a web interface. Installed on a server, it turns that server into a small private cloud which you administer yourself. Learn more →
- Pterodactyl
- Pterodactyl is an open-source game server management panel: it isolates each server in its own container and provides console, files, backups and user management from the browser. It is the reference tool for anyone hosting several game servers on one machine. Learn more →
- Reverse proxy
- A reverse proxy sits in front of one or more servers and receives requests on their behalf, then distributes them. It is used to handle TLS certificates in a single place, to spread load, to cache responses and to hide the real architecture. Nginx, Caddy and Traefik are the most common examples.
- GDPR
- The GDPR is the European regulation on the protection of personal data. For hosting, it mainly means knowing where the data physically resides and who can access it: servers located in France, operated by a French company, make demonstrating compliance considerably simpler.
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