In today’s world, where digital technologies penetrate every sphere of life, the stable operation of IT infrastructure is not just a desirable condition — it is a critical necessity. Whether it’s a small website, a large online store, a mobile application, or an internal corporate system — any failure can lead to serious losses, reputational damage, and user dissatisfaction. This is where monitoring steps in.

What is Monitoring and Why Is It Important?

Monitoring in IT is the continuous collection, analysis, and visualization of data about the state and performance of infrastructure, applications, and services. Imagine you have a complex machine, like a car. To keep it running smoothly, you regularly check fuel level, oil, tire pressure. Monitoring serves the same purpose for servers, databases, networks, and applications.

Why is it important?

• Early problem detection: Monitoring allows you to notice early signs before they grow into critical failures. For example, disk space is running out or error rates are rising.
• Performance optimization: Collecting data on CPU load, memory usage, or DB response time helps identify bottlenecks and optimize the system.
• Resource planning: Trend analysis helps predict when scaling will be needed and prepare in advance.
• Increased availability: The sooner you know about a failure, the faster you can fix it.
• Security: Unusual activity or traffic spikes can indicate attacks or other threats.

Main Types of Monitoring

There are many types of monitoring. Here are the key categories:

• System monitoring: Tracking basic parameters of servers and VMs — CPU load, RAM usage, disk occupancy, network traffic, uptime.
• Network monitoring: Monitoring routers, switches, network paths, packet loss levels, and latency.
• Application monitoring (APM — Application Performance Monitoring): Analyzing application performance: response time, DB queries, exceptions, function logic.
• User monitoring:
  • RUM (Real User Monitoring) — tracking actual user behavior.
  • Synthetic Monitoring — simulating user actions to check availability and response time from different regions.

Key Metrics: What to Watch First?

Here are the most important metrics to monitor:

• CPU Usage: Processor load. High levels may indicate overload or coding issues.
• Memory Usage: RAM usage. Memory leaks greatly affect performance.
• Disk I/O: Read/write activity. High values can signal storage issues.
• Network Throughput: Amount of transmitted/received data. Helps understand network load.
• Uptime: Time without failures.
• Latency: Response delays. Crucial for web applications and user experience.
• Error Rate: Share of failed requests. A sudden spike means immediate investigation.

Alerts and Notifications: When the System Sounds the Alarm

Collecting data is useful, but reacting to failures quickly is even more important. That’s where alerts come in — notifications triggered when metrics deviate from the norm.

A good alerting system should be:

• Relevant: Not overload the team with noise.
• Timely: Warn as early as possible.
• Informative: Provide enough data for diagnostics.
• Targeted: Reach the right specialists.

Monitoring systems are often integrated with Telegram, Slack, email, SMS, PagerDuty, and other alerting services.

What’s Next?

In the following articles, we will explore popular monitoring tools that help build a reliable control system:

• Munin — a simple tool for basic monitoring.
• Prometheus + Node Exporter + Grafana — a powerful stack for cloud and containerized environments.
• Zabbix Agent + Zabbix Server — an all-in-one comprehensive solution.
• VictoriaMetrics + Grafana — an efficient time-series storage with PromQL query support.

Each tool has its strengths and specifics. In upcoming materials, we’ll help you choose the best one for your infrastructure.