Monitoring comes with its own vocabulary. Understanding these terms is essential for effective communication.
This glossary covers the most common terms in uptime monitoring and availability management.
Use it as a reference when discussing SLAs, incidents, or monitoring strategies.
Disponibilité de Base
- Uptime
- Temps pendant lequel un service est opérationnel et accessible. Opposé de downtime.
- Downtime
- Temps pendant lequel un service est indisponible ou non fonctionnel.
- Availability (Disponibilité)
- Pourcentage de temps où le service est opérationnel. Uptime / (Uptime + Downtime) × 100.
- Nines (Les "neuf")
- Façon d'exprimer la disponibilité. 99.9% = "trois nines", 99.99% = "quatre nines".
SLA, SLO, SLI
- SLA (Service Level Agreement)
- Contrat définissant le niveau de service promis au client, avec pénalités en cas de non-respect.
- SLO (Service Level Objective)
- Objectif interne de niveau de service. Plus strict que le SLA pour avoir une marge.
- SLI (Service Level Indicator)
- Métrique mesurant le niveau de service. Ex: pourcentage de requêtes < 200ms.
- Error Budget
- Quantité de downtime "autorisé" par le SLO. 99.9% SLO = 0.1% d'error budget.
Métriques de Fiabilité
- MTTR (Mean Time To Recover)
- Temps moyen entre la détection d'un incident et sa résolution.
- MTTD (Mean Time To Detect)
- Temps moyen entre le début d'un incident et sa détection.
- MTBF (Mean Time Between Failures)
- Temps moyen entre deux incidents. Mesure de la fiabilité globale.
- MTTA (Mean Time To Acknowledge)
- Temps moyen entre la réception d'une alerte et sa prise en charge.
Frequently Asked Questions
What's the difference between uptime and availability?
Often used interchangeably. Technically, availability = uptime / total time, expressed as percentage.
How do I calculate downtime from availability?
(1 - availability) × time period. For 99.9% monthly: 0.001 × 30 days × 24h = 43 min downtime.
Is 99.9% uptime good enough?
Depends on your business. 99.9% means ~8.7 hours/year downtime. E-commerce may need higher.
What's a typical MTTD for good monitoring?
With proper monitoring like MoniTao, MTTD can be under 1 minute for HTTP checks.
Speak the Language
Understanding these terms helps you communicate with your team, vendors, and stakeholders.
MoniTao helps you improve all these metrics: reduce MTTD, increase uptime, meet your SLOs.
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