Service level indicators

A Service level indicator (SLI) is a unique metric used to measure the performance or reliability of a service. It serves as the foundation for defining the service level objectives (SLOs) and helps quantify aspects such as availability, latency, throughput, and error rate.

In Site24x7, SLIs are derived from real-time monitoring data collected from various sources, such as website monitors, server monitors, application performance monitoring (APM), network monitors, and so on.

How can SLIs be determined?

SLIs are determined by selecting relevant key performance indicators (KPIs) from existing monitors. Some of the SLIs include availability, latency, response time, throughput, and memory usage. These reflect customer-impacting parameters and are used to evaluate service health. Site24x7 offers three different evaluation methods to calculate SLIs: time-based evaluation, time-slice-based evaluation, and count-based evaluation. Let's look into each, along with examples.

Consider, you're monitoring your DNS server to ensure users can resolve domain names without failure.

• Time-based evaluation tracks how long a service remains healthy during a specific period.
  • Example: Your DNS server was continuously monitored over the last 24 hours. It stayed up and responded correctly for 23 hours. Based on this, your SLI would be the uptime of your DNS server.
• Time-slice-based evaluation divides time into intervals and checks whether the service meets the expected standard in each slice.
  • Example: You monitor the DNS server every hour throughout the day. Out of the 24 hourly checks, the server met performance expectations (i.e., fast response and no errors) during 20 of those intervals. So, your SLI would be the value of the successful time slices.
• Count-based evaluation calculates the ratio of successful events to the total number of events.
  • Example: Over the course of the day, you sent 100 DNS queries to the server. 95 of them received valid, timely responses, while 5 failed or timed out. The resulting SLI is (95/100) × 100 = 95% success rate.

By selecting the right indicators and methods of evaluation, you can set measurable, realistic goals for your services, track real-time performance, and ensure customer satisfaction. With flexible configuration options and comprehensive insights, SLIs in Site24x7 empower you to proactively manage service quality and stay aligned with your service-level commitments.

Related articles

• Overview of SLO
• Add an SLO