Dedicated Server Glossary

Infrastructure terminology is full of words that sound precise and mean nothing in particular. Unlimited bandwidth. Enterprise-grade. High performance. This dedicated server glossary does the opposite: every entry contains a number, a threshold, or a specific mechanism, and every entry says what it does not cover.

Where a figure changes over time, we say when it was measured. If the industry disagrees, we say so. And when a term exists to obscure rather than clarify, we say that too.

This glossary is maintained continuously. Figures are accurate as of the date last updated. Where a measurement changes over time, the year of measurement is stated in the entry.

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Adaptive bitrate

A streaming method in which the same video is encoded at several resolutions and bitrates, called a ladder, and the player switches between rungs as the viewer’s connection changes. It protects against buffering, and it multiplies encoding work: a four-rung ladder means four encodes for every live stream. HLS and DASH are the common delivery formats. See Video Transcoding Server: CPU, GPU, and What to Check Before You Rent

AMS-IX

The Amsterdam Internet Exchange, one of the largest internet exchange points in the world. As of 2026 it carries peak traffic above 15 terabits per second across several hundred connected networks. Direct peering at AMS-IX removes intermediate transit hops between a Netherlands server and most European ISPs, which reduces both latency and its variance. It does not reduce the physical distance, which sets the floor. See Dedicated Server Netherlands.

Anycast

A routing method in which one IP address is announced from multiple physical locations, and BGP delivers each user to the topologically nearest one. Used by DNS resolvers and CDN edge networks. Anycast reduces latency for stateless requests. It works poorly for long-lived TCP sessions, because a routing change mid-session breaks the connection.

AppArmor and SELinux

Mandatory access control frameworks that confine processes to a declared set of permitted operations, so that a compromised service cannot exceed its profile. AppArmor is Ubuntu’s default and is path-based; SELinux is the Red Hat family’s default and is label-based. Neither is more secure in principle. SELinux is more expressive and harder to configure correctly, which in practice means it is more often disabled. See Ubuntu Server for Dedicated Hosting.

Attack surface

The total set of points at which an unauthorised party could interact with a system: open ports, running services, user accounts, installed packages, exposed endpoints. Hardening is the process of shrinking it. Every service that is not running cannot be exploited, regardless of what vulnerabilities it contains.

ASIC

Application-specific integrated circuit: a chip built for one job. In video, ASIC transcoders such as the AMD MA35D and NETINT’s Quadra VPU are designed to run many real-time streams per card at low power, in exchange for less flexibility than a CPU. See Hardware Transcoder: GPU, ASIC or CPU? How to Compare Them

Autonomous System Number (ASN)

A globally unique identifier assigned to a network that controls its own routing policy. Data centres, ISPs, and large hosting providers each operate under an ASN. Analysing the ASN distribution of inbound traffic is one of the more reliable ways to separate residential users from data-centre-originated bot traffic.

Bandwidth

The maximum rate at which data can transfer, measured in bits per second. A 1 Gbps interface tops out at roughly 125 MB/s in ideal conditions, before protocol overhead. Bandwidth is not speed. A page that issues twenty sequential requests over a 200ms latency link loads slowly regardless of how wide the pipe is. See What Is Network Bandwidth.

Bare metal

A physical server dedicated to a single tenant, with no hypervisor between the operating system and the hardware. Containers running on bare metal avoid the virtualisation overhead present on a VM host. The term is often used loosely by providers who mean dedicated instance on shared hardware, which is not the same thing. See What Is a Bare Metal Server.

Bitrate

The amount of data used for each second of video, usually measured in megabits per second (Mbps). It decides file size and the bandwidth a viewer needs: 6 Mbps comes to about 2.7 GB an hour, and a stream that needs more than the viewer’s connection supplies will buffer. Higher bitrate generally means better quality, up to a point of diminishing returns. See What Is Video Transcoding? A Complete Beginner’s Guide

BGP

Border Gateway Protocol, the mechanism by which autonomous systems announce which IP ranges they can reach. BGP selects paths by policy and AS-path length, not by latency. A geographically short route can therefore be slower than a longer one if the peering arrangements are poor, which is why data-centre network quality matters as much as its coordinates.

Brute force attack

Automated attempts to guess credentials by exhaustive trial. Against SSH, this is continuous background noise on any server with a public IP address. The asymmetry is total: the defender must block every attempt, the attacker needs one success. Key-based authentication does not mitigate brute force. It renders it arithmetically irrelevant. See SSH Security: Brute Force Protection.

Buffer pool

The region of RAM in which a database engine caches table and index pages. When the working dataset fits in the buffer pool, queries execute from memory in microseconds. When it does not, every miss becomes a storage read. This is the mechanism by which RAM, not CPU, becomes the first bottleneck in the majority of web application workloads. See Understanding RAM Usage in Web Hosting.

Caching layers

Object caching: Redis, Memcached, stores computed values and query results in memory, eliminating repeated database work. Full-page caching: Varnish, Nginx, stores complete HTML responses, so a cache hit executes no application code at all. A site with a 90% full-page hit rate reduces application CPU for that content by roughly 90%. Personalised and authenticated content is largely uncacheable, which is why dynamic-heavy applications see smaller gains. See Server Caching Explained.

CDN

Content delivery network: a group of servers spread across locations that cache files, such as video segments, and serve them close to viewers. It keeps the original server from answering every request, which is how live audiences scale past a single port. See RTMP vs HLS: Which Protocol Fits Your Live Stream?

Codec

The method that compresses video, or audio, for storage and sending, and decompresses it for playback; the name joins coder and decoder. H.264 is the most compatible, HEVC can halve file size but depends on the device and platform, and AV1 is royalty-free and compresses as much as 50% better than H.264, according to MDN. A codec is not a file type: the container, such as MP4 or WebM, holds the compressed streams. See What Is Video Transcoding? A Complete Beginner’s Guide

Colocation

Renting rack space, power, cooling, and network connectivity in a data centre, while owning the hardware yourself. Maximum control, maximum capital expenditure, and full responsibility for hardware failure. Dedicated server rental transfers the hardware risk to the provider. See What Is Colocation Hosting.

Core Web Vitals

Google’s set of user-experience metrics used as a ranking signal, measured from field data collected in Chrome. Comprises LCP, INP, and CLS. Critically, the ranking signal uses the mobile measurement, not the desktop one, because of mobile-first indexing. See Why Mobile Is Slower Than Desktop.

CPU utilisation vs load average

Utilisation is the percentage of processor capacity in use. Load average counts processes running or waiting to run. They answer different questions. A load average of 8.0 on a 16-core server is comfortable. The same figure on a 4-core server means every core is saturated with two processes queued behind each. Utilisation tells you the CPU is busy; load average tells you whether work is waiting. See What Is Server Load.

crUX

CrUX (Chrome User Experience Report), Google’s public dataset of real-user performance metrics collected anonymously from Chrome, aggregated over a rolling 28-day window. It is the actual data source behind every Core Web Vitals score; PageSpeed Insights and Search Console both read from it rather than running a fresh test. CrUX only reflects Chrome users, so a site whose audience is mostly Safari or Firefox may have thin or missing CrUX data despite real traffic. Pages or origins below a minimum traffic threshold receive no CrUX data at all, and Google falls back to lab-based estimates in that case.

Cumulative Layout Shift (CLS)

Measures unexpected visual movement of page elements during load. Google’s threshold for good is below 0.1. CLS is almost entirely a front-end concern, unreserved image dimensions, late-injected banners, and infrastructure has essentially no influence on it.

CVE

Common Vulnerabilities and Exposures: the public identifier for a known security flaw, such as CVE-2026-109618. Vendors, advisories and scanners use it to refer to the same bug. See PHP Vulnerability: What PHP2Shell Is and How to Patch It

CVSS

Common Vulnerability Scoring System: a 0 to 10 scale for the severity of a flaw. Scores from 9.0 are critical. PHP rates both PHP2Shell flaws 9.2 on CVSS v4.0. See PHP Vulnerability: What PHP2Shell Is and How to Patch It

Data residency

The requirement that data be stored and processed within a defined jurisdiction. Hosting inside the EEA satisfies GDPR residency by geography, without Standard Contractual Clauses or transfer impact assessments. On multi-region cloud infrastructure, replication and support access can move data across borders in ways that require deliberate configuration to prevent.

DDoS

A distributed denial-of-service attack, in which many hosts flood a target with traffic to exhaust its capacity. Volumetric attacks saturate bandwidth; application-layer attacks exhaust CPU or connection tables with comparatively little traffic. Server hardening does not defend against volumetric DDoS, which must be absorbed upstream of the server. See What Is a DDoS Attack.

Dedicated server

A physical server whose resources serve one tenant exclusively. No hypervisor, no shared CPU, no noisy neighbours, and full root access. Cost is fixed monthly regardless of utilisation, which makes it economical for stable continuous workloads and uneconomical for genuinely bursty ones. See What Is a Dedicated Server.

Default-deny firewall

A firewall policy in which all inbound traffic is rejected unless explicitly permitted. The inverse — permitting everything and blocking known threats — fails the moment an unanticipated service starts listening. A web server needs ports 80 and 443. Databases belong on the loopback interface. See What Is a Firewall.

ECC RAM

Error-Correcting Code memory, which detects and transparently corrects single-bit errors and detects multi-bit errors. Consumer RAM does neither. Silent bit-flips in a database buffer pool corrupt data without any error surfacing until much later. ECC is standard on server-class hardware and is one of the least glamorous reasons enterprise hardware costs more.

EEA

EEA (European Economic Area) extends the EU’s single market to include Iceland, Liechtenstein, and Norway alongside all EU member states, applying the same free movement of goods, services, and data protection standards. For GDPR purposes, transferring personal data within the EEA carries no additional legal requirement, the same protection applies throughout. Transferring data outside the EEA requires a legal transfer mechanism, Standard Contractual Clauses or an adequacy decision, that hosting entirely within the EEA avoids by removing the question altogether.

Egress fees

Charges levied by a provider for data leaving its network. Major cloud providers bill outbound transfer per gigabyte, typically around $0.09/GB in common regions, with a small monthly free allowance. Inbound transfer is usually free. Egress is the line item that most often makes cloud infrastructure unexpectedly expensive at scale, and it has no equivalent on unmetered dedicated bandwidth. See AWS vs Dedicated Server: Full Cost Breakdown.

Encoder

The software or hardware that compresses raw video into a stream a server can accept. OBS and FFmpeg are common software encoders, and a GPU or a dedicated chip can do the same job in hardware. For live video, the encoder also decides the bitrate, the keyframe interval and the protocol. See What Is RTMP? Real-Time Messaging Protocol Explained

Enhanced RTMP

Enhanced RTMP, or E-RTMP, is an open update to RTMP and FLV published by the Veovera Software Organization, with contributors including Adobe, Google, Twitch, FFmpeg and OBS. It adds HEVC, AV1, VP9 and Opus, HDR and multiple tracks per stream, and keeps compatibility with existing RTMP servers. See What Is RTMP? Real-Time Messaging Protocol Explained

fail2ban

A daemon that parses authentication logs, identifies IP addresses producing repeated failures, and blocks them at the firewall. The stock configuration bans an address for ten minutes after five failed attempts. It reduces log noise and blunts distributed attacks. It does not replace key authentication, and layering it over password authentication is treating a symptom.

Federation

The way separate servers running the same software follow each other and share content. PeerTube instances federate through ActivityPub, so a video on one server can reach users and follow lists on another. See PeerTube Hosting: What It Needs and What to Run It On

FFmpeg

The open-source command-line tool that decodes, converts and encodes almost any audio or video format. It runs software encoders such as x264 and x265 on the CPU, and it can hand work to hardware encoders such as NVENC. Its progress line prints a speed figure, where 1.0x means real time, which makes it the simplest way to measure how fast a server transcodes. See Video Transcoding Server: CPU, GPU, and What to Check Before You Rent

FPGA

Field-programmable gate array: a chip whose circuits can be reconfigured after manufacture. In video, FPGAs are one of the three kinds of hardware transcoder, alongside GPUs and ASICs, and they can be reprogrammed for new codecs in a way a fixed ASIC cannot. See Hardware Transcoder: GPU, ASIC or CPU? How to Compare Them

GDPR

The EU General Data Protection Regulation. It does not mandate hosting in any specific country. It restricts transfers of EU residents’ personal data outside the EEA unless a legal transfer mechanism exists. A server in an EU member state removes the question rather than answering it. See Dedicated Servers and GDPR.

HDD

Hard disk drive, a storage device that keeps data magnetically on spinning platters, read and written by a moving head. A random read takes roughly 10 to 20 ms because the head must move, against about 0.1 ms on a SATA SSD, which is why HDDs are the wrong choice for operating systems and databases. Their strength is capacity per euro: drives of 20 TB and more suit backups, archives, and bulk media. An HDD is not obsolete, only specialised. See What Is HDD?

Health Check

A periodic request a load balancer sends to each backend server to verify it is still serving correctly. Machines that fail leave the rotation automatically and rejoin when they recover. A naive health check requests a static file and confirms only that the web server responds. A useful one exercises the database connection, because a machine whose database has failed still returns static files perfectly.

High availability

An architecture designed to survive component failure without service interruption, typically through redundancy and automatic failover. High availability is not a hardware specification; it is a system property. A single server, however well specified, is a single point of failure by definition. See High Availability Hosting Explained.

HLS

HTTP Live Streaming: a protocol that splits a stream into short video files, usually a few seconds long, plus a playlist that tells the player which one to fetch next. It runs over ordinary HTTP, so browsers, phones and caches handle it easily, and players can switch quality as the connection changes. It adds delay by design: the specification keeps players at least three segment lengths behind live by default. See Nginx RTMP Server: How to Set It Up and What to Run It On

Hyper-threading

Intel’s implementation of simultaneous multithreading, presenting each physical core as two logical processors. A 20-core Xeon reports 40 threads. Throughput gains for mixed workloads typically fall in the 15 to 30% range, not 100%. For workloads that saturate the execution units of a single core, hyper-threading provides close to nothing.

Hypervisor

Software that creates and runs virtual machines. Type 1 runs directly on hardware (KVM, VMware ESXi, Proxmox). Type 2 runs on top of a host operating system. Every hypervisor introduces some overhead; on modern hardware with virtualisation extensions this is small for CPU and larger for I/O. See What Is Server Virtualization.

I/O wait

The percentage of time the CPU sits idle waiting for a storage operation to complete, visible as wa in top or vmstat. High I/O wait alongside high load average usually means the bottleneck is storage, not the processor. Adding CPU cores to a server with 30% I/O wait changes nothing. See Disk I/O Bottleneck Explained.

Ingest

The first leg of a live stream: the connection that carries video from an encoder into a server or platform. RTMP and RTMPS are the usual ingest protocols, and HLS or SRT can also do it. After ingest, the platform transcodes the stream and delivers it to viewers over a different protocol. See What Is RTMP? Real-Time Messaging Protocol Explained

Interaction to Next Paint (INP)

Measures responsiveness to user input across the whole page lifecycle, replacing First Input Delay. Google’s threshold for good is below 200ms. INP is dominated by JavaScript main-thread work, so a fast server improves it only indirectly, by not delaying script execution.

IPv6

IPv6 (Internet Protocol version 6) is the current standard for addressing devices on the internet, using 128-bit addresses instead of IPv4’s 32-bit scheme. This expands the available address space to a number large enough that exhaustion is not a practical concern, unlike IPv4’s roughly 4.3 billion addresses, which are now fully allocated. Most production servers run dual-stack, with both IPv4 and IPv6 active simultaneously, since a meaningful share of visitors still connect over IPv4-only networks.

Internet Exchange Point (IXP)

A physical facility where networks interconnect directly rather than routing through a paid transit provider. AMS-IX in Amsterdam, DE-CIX in Frankfurt, and LINX in London are the largest in Europe. A server in a data centre with dense IXP presence reaches European users in fewer hops than the same hardware in a poorly peered facility. See How Server Location Affects Website Speed.

IOPS

Input/output operations per second. Manufacturer figures almost universally assume 4 KB blocks at queue depth 32, with whichever access pattern flatters the device. Real database workloads rarely match those conditions, and observed IOPS two to five times below the specification sheet is common rather than exceptional. Treat published IOPS as a ceiling, never as a forecast. See NVMe and RAID for High-IOPS Workloads.

IPMI

Intelligent Platform Management Interface, an out-of-band management channel that operates independently of the server’s operating system and main network interface. It provides remote power cycling, console access, and hardware sensor readings even when the OS has failed to boot. IPMI is what recovers a server after a firewall rule locks you out. Its own interface should never be exposed to the public internet.

Keyframe

A video frame stored in full, so a player can start decoding from it without any earlier frame. Encoders insert one every few seconds, and HLS cuts its segments at keyframes, so the keyframe interval sets the shortest segment you can make. See Nginx RTMP Server: How to Set It Up and What to Run It On

Largest Contentful Paint (LCP)

The time until the largest visible content element renders. Google’s threshold for good is under 2.5 seconds. LCP inherits TTFB entirely: a 900ms server response leaves 1.6 seconds for everything else. Infrastructure influences LCP more than any other Core Web Vital.

Latency

The time for a signal to travel from source to destination. In fibre, light propagates at roughly two-thirds of its vacuum speed, approximately 200,000 km per second, which imposes about 1ms of round-trip latency per 100km of cable, before any routing overhead. Amsterdam to London measures 5 to 10ms in practice; Amsterdam to New York, 70 to 90ms. No amount of hardware or software optimisation reduces this floor. See Latency Explained.

Layer 4 load balancing

Layer 4 load balancing routes on IP addresses and TCP or UDP ports without inspecting traffic content, processing millions of packets per second with minimal added latency. So, Layer 7 inspects the full HTTP request, including URL, headers, and cookies, enabling content-based routing, SSL termination, and application-aware health checks, at the cost of higher processing overhead. Most web applications need Layer 7.

LL-HLS

Low-Latency HLS: an extension of HLS that splits each segment into parts shorter than a second, so players can start closer to live. Apple announced it in 2019 and added it to the HLS specification in 2020, and it needs HTTP/2. See RTMP vs HLS: Which Protocol Fits Your Live Stream?

Load Balancer

A device or software component that sits between clients and a pool of backend servers, receiving every request and routing it to one of them according to a defined algorithm. The load balancer becomes the address that DNS resolves to, which means it also becomes a single point of failure unless deployed as a redundant pair. It distributes work; it does not make the work faster.

Managed vs unmanaged

Unmanaged means the provider delivers working hardware, network, and an operating system image. Everything above that is yours, patching, security, backups, monitoring. Managed means some subset of that is theirs. The boundary is never standardised, and the correct question is not is it managed but which specific tasks are contractually theirs. See Managed vs Unmanaged Hosting.

MTBF

Mean Time Between Failures, the average operating time between one failure and the next on repairable equipment: total operating time divided by the number of failures. A server fleet that logs 3 failures over 45,000 operating hours has an MTBF of 15,000 hours, about 20 months. It describes a population average, not the life of any single machine, and it says nothing about how long each failure takes to fix, which is MTTR. Together they set availability: MTBF ÷ (MTBF + MTTR). See What Is MTTR?

Mean Time To Recovery (MTTR)

The average time to restore service after a failure. In practice, MTTR is determined less by hardware and more by whether the team can find the runbook, knows the firewall rules, and has tested the restore procedure. It is the metric most improved by documentation and least improved by expenditure. See What Happens When a Server Crashes. The acronym is also used for mean time to repair, respond, and resolve, which start and stop the clock at different points; recovery, the whole outage from failure to restored service, is the version users experience. See What Is MTTR?

NAND flash

The memory type inside almost every SSD. It stores bits as electrical charge in cells, writes data in pages, and erases it only in whole blocks, which is why an SSD needs a controller to spread wear and reclaim space. A cell holds one to five bits (SLC, MLC, TLC, QLC, PLC), and more bits per cell mean a lower cost per gigabyte but lower endurance and speed. NAND keeps data without power, unlike RAM, and it is not infinitely rewritable. See What Is SSD?

Noisy neighbour

The performance degradation one tenant experiences because another tenant on the same physical host is consuming shared CPU, memory bandwidth, or storage I/O. The defining characteristic is that your own metrics move without your own traffic changing. Diagnosing it from inside the guest is close to impossible, which is the practical case for single tenancy. See What Causes High CPU Usage.

NUMA

Non-Uniform Memory Access. On a dual-socket server, each processor has memory attached directly to it. A core accessing memory on its own socket is faster than one reaching across the interconnect to the other socket’s memory. Workloads that are not NUMA-aware can lose measurable performance on dual-socket hardware relative to a well-specified single-socket machine.

NVENC

NVIDIA’s dedicated hardware video encoder, built into most GeForce, RTX and data centre GPUs. It encodes H.264 and HEVC without loading the CPU, and AV1 from the Ada generation onward. The number of units differs by card: an RTX 4090 has 2 and an L40S has 3, while compute-only GPUs such as the H100 and A100 have none. GeForce cards cap concurrent sessions at 12 in NVIDIA’s current matrix, and most professional and data centre cards have no cap. See Video Transcoding Server: CPU, GPU, and What to Check Before You Rent

NVMe

Non-Volatile Memory Express, a storage protocol that addresses SSDs over PCIe rather than through the SATA controller. SATA III caps at 6 Gbps, or roughly 550 MB/s in practice. NVMe removes that ceiling and, more importantly, supports far deeper command queues, which is where database workloads actually benefit. See How NVMe Storage Boosts Performance.

Object storage

Storage that keeps files as objects in a bucket reachable through an S3-compatible API, instead of on a fixed disk. PeerTube can store its videos this way, so capacity grows without resizing a disk. See PeerTube Hosting: What It Needs and What to Run It On

Origin server

The server that holds the original copy of the content, and that caches or CDNs fetch it from. In live streaming, it receives the stream from the encoder and packages it for viewers. See RTMP vs HLS: Which Protocol Fits Your Live Stream?

P2P (peer-to-peer)

A way of delivering data where viewers pass pieces of a video to each other instead of fetching everything from the server. PeerTube uses it to cut the server’s bandwidth, and in its own stress test it saved 75% of it on a live stream in the best case. See PeerTube Hosting: What It Needs and What to Run It On

Peering

An arrangement in which two networks exchange traffic directly, usually without payment. The alternative is transit, which is paid. A provider with extensive peering delivers lower and more consistent latency to the networks it peers with. Peering quality is invisible from a specification sheet and only becomes apparent under measurement.

PHP-FPM

PHP FastCGI Process Manager: a service that runs PHP in a pool of worker processes behind a web server such as Nginx or Apache. It is the usual way to serve PHP today, and each worker handles many requests in turn. See PHP Vulnerability: What PHP2Shell Is and How to Patch It

Power-loss protection

A feature of enterprise SSDs that lets a drive finish the writes it has already accepted when power drops. Onboard capacitors supply the energy to flush data held in the drive’s cache to flash. Consumer SSDs usually leave it out, so data still in the cache during a power cut can vanish. It matters most for databases and any workload where a half-written transaction would leave data inconsistent. It does not replace a UPS, RAID, or tested backups. See Consumer SSD in a Server

Principle of least privilege

Every account, process, and credential should hold exactly the permissions its function requires, and nothing further. An application’s database user should read and write its tables; it should not be able to drop them or create users. NSA and CISA red teams identify improper separation of user and administrator privilege among the most common misconfigurations found in large organisations.

Provisioning

The process of preparing and delivering a server so that it is ready to use: installing the operating system, configuring the network, assigning IP addresses, and granting access. Provisioning time ranges from minutes on automated platforms to a few hours where hardware is configured to order. It is a one-time event at the start of the contract, distinct from the ongoing management that follows.

Quick Sync

Intel’s hardware video encoder and decoder. It runs in Intel’s integrated graphics and in its Arc GPUs, and Intel lists no integrated graphics for the Xeon Gold 5215 and 6138 processors used in Swify’s standard plans. In a November 2025 academic test, Quick Sync on an Arc GPU saved about 5% of bitrate against the best software preset that could run in real time. See Hardware Transcoder: GPU, ASIC or CPU? How to Compare Them

Rack unit (RU)

A unit of server height in a rack: 1RU is 1.75 inches (4.45 cm). A 2RU server is twice that height and a 4RU server four times, which decides how many cards, fans and drives fit inside. See Hardware Transcoder: GPU, ASIC or CPU? How to Compare Them

RAID 0

Data striped across multiple drives with no redundancy. Capacity and throughput scale with drive count; so does failure probability. One drive failure destroys the array. RAID 0 is appropriate for scratch data and reproducible caches, and for nothing else in production.

RAID 1

Data mirrored across two drives. Half the raw capacity is usable. One drive can fail without data loss or interruption. This is the correct default for production servers where downtime is unacceptable. RAID 1 is not a backup: it faithfully mirrors an accidental DROP TABLE to both drives instantly. See What Is RAID.

RAID 10

Mirrored pairs, striped. Requires a minimum of four drives and yields half the raw capacity. Combines RAID 1’s redundancy with RAID 0’s throughput, and rebuilds far faster than parity-based levels. The standard choice for write-heavy database workloads that can afford the capacity cost.

Remote code execution (RCE)

A flaw that lets an attacker run their own code on a server from across the network. When it needs no login, it is called unauthenticated RCE, and it is usually rated critical. See PHP Vulnerability: What PHP2Shell Is and How to Patch It

RTMP

Real-Time Messaging Protocol, a long-established protocol for sending a live video stream from an encoder to a server. OBS and most hardware encoders can push RTMP, and YouTube accepts it for live ingest, with RTMPS as the encrypted variant. A transcoding server usually receives RTMP in, then produces the renditions that viewers watch.

See Video Transcoding Server: CPU, GPU, and What to Check Before You Rent

See Nginx RTMP Server: How to Set It Up and What to Run It On

RTMPS

RTMP inside a TLS connection, so the stream and the stream key are encrypted in transit. Platforms such as YouTube recommend it over plain RTMP, and it commonly runs on port 443. The nginx-rtmp-module does not support it natively and needs a TLS proxy such as HAProxy or stunnel in front of it. See What Is RTMP? Real-Time Messaging Protocol Explained

Round-Trip Time (RTT)

The interval for a packet to reach a destination and for the acknowledgement to return. Every stage of a page load pays RTT independently: the TCP three-way handshake costs one RTT, a TLS 1.3 handshake costs one more, and each subsequent request costs at least one. TLS 1.2 costs two. Twenty round trips at 100ms is two seconds of pure waiting. See How TCP/IP Works.

RPO and RTO

Recovery Point Objective is how much data you can afford to lose, expressed as time, hourly backups imply a one-hour RPO. Recovery Time Objective is how long restoration may take. These two numbers determine the backup architecture. Choosing them explicitly, before an incident, is the entire exercise. See Why Regular Backups Matter.

SATA SSD

A solid-state drive connected over the SATA interface. Eliminates the mechanical seek latency of spinning disks, the single largest performance improvement available to a database server, but remains bounded by the SATA III ceiling of roughly 550 MB/s. Adequate for most web workloads. The constraint becomes visible under sustained high-IOPS database load.

Segment

A short video file, usually a few seconds long, that HLS and similar formats use to deliver a stream. A playlist lists the segments in order, and the player downloads them one by one. Shorter segments reduce the delay behind live, but they shrink the buffer. See RTMP vs HLS: Which Protocol Fits Your Live Stream?

Server hardening

The deliberate reduction of a system’s attack surface: removing default credentials, disabling unused services, restricting privilege, applying patches promptly, and replacing permissive defaults with restrictive configuration. Hardening is a continuous process, not a provisioning task. A server hardened once and never reviewed drifts back toward its defaults as software accumulates. See What Is Server Hardening.

Service Level Agreement (SLA)

A contractual commitment to a service level, usually uptime, with defined remedies when it is missed. Read the remedy clause: most SLAs compensate with service credits proportional to the outage, not with damages proportional to your revenue loss. An SLA is a statement of confidence, not an insurance policy. See Understanding Server Uptime SLAs.

Session Persistence

Routing a user’s requests consistently to the same backend server for the duration of their session, so that locally stored state remains reachable. Also called sticky sessions. It distributes load unevenly whenever some users hold longer sessions than others, and it undermines failover, because a machine failure destroys the sessions living on it. Moving session state into a shared Redis instance removes the need for it entirely.

Setup fee

A one-time charge some providers apply when provisioning a new server, separate from the recurring monthly price. It covers the initial hardware configuration and deployment. Not every provider charges one, and its presence or absence is worth checking before signing, because a low monthly price paired with a high setup fee can cost more in the first year than a higher monthly price with no setup fee.

Shared hosting

Many websites on one physical server, isolated by user accounts rather than by hardware. Resources are pooled and capped per account. It is inexpensive, and its failure mode is that your performance depends on the behaviour of tenants you cannot see or influence. See Outgrowing Shared Hosting.

Single-socket vs dual-socket

A single-socket server has one physical CPU; a dual-socket server has two, doubling core count and memory channels. Dual-socket suits virtualisation hosts and parallel workloads that scale across many cores. Most web applications perform better on a high-specification single socket than on a lower-specification dual socket at the same price, because per-core performance matters more than total core count, and because NUMA introduces complexity that gains nothing if the workload cannot exploit it. See How to Choose the Right CPU.

SLC cache

A portion of an SSD’s flash that the drive writes in single-bit (SLC) mode to absorb bursts of writes, then moves to its denser cells, which store three or four bits. Consumer SSDs rely on it to look fast: while the cache has room, writes are quick. According to SNIA, small bursty workloads that stay inside the cache see great performance and endurance, while a workload that writes continuously spills out of it and loses that advantage. See Consumer SSD in a Server

SMART

Self-Monitoring, Analysis and Reporting Technology, the health counters built into drives. Hard drives report reallocated and pending sectors, and SSDs report data written and the share of rated endurance used (the percentage_used field on NVMe). Reading them on two days shows how fast a drive is wearing, and rising error counts are an early warning of failure. SMART does not catch every failure, so it complements backups rather than replacing them. See Consumer SSD in a Server

SSD

Solid-state drive, a storage device that keeps data in NAND flash memory instead of on spinning platters. With no moving parts, a SATA SSD answers a random read in about 0.1 ms, against 10 to 20 ms for a hard drive. The interface, SATA or NVMe, sets the speed ceiling, and the endurance rating, TBW or DWPD, sets how much data the drive can absorb, because every flash cell survives only a finite number of writes. An SSD does not remove the need for backups: it gives no audible warning before it fails. See What Is SSD?

SSH key authentication

Authentication using an asymmetric key pair rather than a password. An ed25519 key cannot be brute-forced within any meaningful timescale; a password can. Disabling PasswordAuthentication in /etc/ssh/sshd_config is the single highest-leverage change available on a new server. Verify key login in a second terminal before applying it. See How to Setup a Dedicated Server.

Stream key

The secret part of an RTMP address that tells the server which stream you are publishing. Anyone who has it can publish to that stream, so treat it like a password and check it on the server, for example with an on_publish callback. See Nginx RTMP Server: How to Set It Up and What to Run It On

TBW and DWPD

The two ways vendors state SSD endurance. TBW (terabytes written) is the total data a drive is rated to absorb. DWPD (drive writes per day) is how many times per day you can overwrite the full capacity during the warranty period. They convert into each other: TBW = capacity × DWPD × 365 × warranty years, so a 1 TB drive rated at 1 DWPD for five years carries 1,825 TBW. Both are ratings under a defined workload, and real endurance varies with write pattern and free space. See What Is SSD?

Thread

In processor terms, a thread is a logical stream of execution a physical core can handle. With simultaneous multithreading, one physical core presents two threads, so a 10-core processor reports 20 threads. The two threads share that core’s execution resources, so the second thread adds throughput only when the first leaves resources idle, typically a 15 to 30 percent gain rather than a doubling. A thread is not a second core, and treating reported thread counts as core counts overstates real capacity.

Tier III and Tier IV

Uptime Institute data centre classifications. Tier III is concurrently maintainable, any component can be serviced without stopping operations, and corresponds to roughly 99.98% availability. Tier IV is fault tolerant, sustaining a single unplanned failure without impact, at roughly 99.99%. The tier describes the facility, not your server, and not your application.

Time to First Byte (TTFB)

The interval between the browser issuing a request and receiving the first byte of the response. It comprises DNS resolution, TCP handshake, TLS negotiation, server processing, and the first byte’s transit. Google’s guidance treats TTFB under 800ms as good and above 1800ms as poor. A well-configured dedicated server serving a European audience should achieve 100 to 300ms. See What Is Time to First Byte.

TLS

Transport Layer Security, the cryptographic protocol that encrypts data in transit between a client and server. PCI-DSS 4.0 requires TLS 1.2 as the minimum acceptable version; TLS 1.0 and 1.1 are explicitly prohibited for new implementations. TLS 1.3 removes several legacy cipher suites and reduces handshake round trips, making it the preferred choice where client compatibility allows.

Transcoding

Converting video that is already compressed into another compressed form: a different codec, resolution or bitrate. A live ladder transcodes one incoming stream into several renditions, such as 1080p, 720p and 480p, in real time, while a video-on-demand library transcodes files in batches. Every frame is decoded and encoded again, so a server that cannot keep pace with real time drops viewers. Encoding is the broader act of compressing video, and transcoding is encoding applied to video that was already encoded. See What Is Video Transcoding? A Complete Beginner’s Guide

Transit

Paid access to the wider internet through a provider that carries your traffic to destinations you do not peer with directly. Transit is the fallback when peering does not exist. It works, and it adds hops.

Unmetered vs Unlimited

These are not synonyms, and the industry benefits from the confusion. Unmetered means the provider does not count the volume of data transferred; the constraint is the port speed. A 1 Gbps unmetered port can move roughly 324 TB in a month at full saturation. Unlimited is a marketing term with no technical definition, and is almost always governed by a fair-use clause buried in the terms of service. Ask which one you are buying. See Hidden Costs of Cheap Hosting.

Uptime percentages

The arithmetic is worth internalising, because the marketing relies on it not being. Over a full year: 99% permits 3 days 15 hours of downtime. 99.9% permits 8 hours 45 minutes. 99.99% permits 52 minutes. 99.999% permits 5 minutes. The difference between three nines and four is not a rounding detail; it is a different class of engineering and a different cost structure. See Website Downtime: Impact on Revenue and Trust.

vCPU

A virtual CPU, also written vCore, is the unit of processing a hypervisor presents to a virtual machine. A vCPU usually maps to one thread of a physical core, not to a full core, so a VM advertised with 4 vCPUs may hold roughly the compute of two physical cores under load. On oversubscribed hosts, several vCPUs from different tenants contend for the same physical core, so a vCPU is a claim on processing time, not a guarantee of it. It is a virtualisation concept and does not apply to a dedicated server, where you hold the physical cores directly.

Virtualisation

Partitioning one physical machine into multiple isolated virtual machines, each with its own operating system. Improves hardware utilisation and provides strong isolation. Costs some performance, particularly for storage I/O, and introduces the noisy-neighbour problem when the host is oversubscribed. See Bare Metal vs Virtualized Servers.

VPS

A Virtual Private Server: a virtual machine on shared physical hardware, with allocated CPU, RAM, and storage. Cheaper than dedicated hardware and genuinely isolated at the OS level. Resource allocation is often oversubscribed, meaning the guaranteed figures and the available figures differ under load. See Dedicated Server vs VPS.

VRAM

VRAM (Video RAM), the memory built directly into a GPU, entirely separate from the server’s system RAM. A model’s parameters must fit inside this pool to run at all, and current data-centre GPUs commonly offer 80GB or more per card, several times what a consumer graphics card carries. Adding system RAM does not compensate for insufficient VRAM, because the two pools are physically distinct and a GPU cannot borrow capacity from one to satisfy the other.

Web Application Firewall (WAF)

A filter that inspects HTTP requests and blocks those matching known attack patterns: SQL injection, cross-site scripting, malicious bot signatures, before they reach the application. A WAF operates at layer 7 and complements a network firewall rather than replacing it. It also produces false positives, which is why it needs tuning rather than installation. See What Is a WAF.

Xeon Gold 5215

Intel server processor, 10 physical cores and 20 threads, base clock 2.5 GHz. Suited to workloads where per-core performance and moderate concurrency matter more than raw parallelism.

Xeon Gold 6138

Intel server processor, 20 physical cores and 40 threads, base clock 2.0 GHz. Twice the parallelism of the 5215 at a lower base clock. The correct choice when the workload distributes across many cores: container hosts, build servers, transcoding pipelines, and the wrong one when a single-threaded bottleneck dominates.

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