Reliability

Introduction Disaster Recovery (DR) is the process, policies, and procedures for recovering and continuing technology infrastructure after a disaster. A disaster can be natural (earthquake, flood), technical (data center failure, ransomware), or human-caused (accidental deletion, security breach). Core Principle: “Hope is not a strategy. Plan for failure before it happens.” Key Concepts RTO vs RPO Time ─────────────────────────────────────────────────────────────> │ │ │ │ Disaster Detection Recovery Normal Occurs Time Begins Operations │◄──────────────────────────────────►│ │ Recovery Time │ │ Objective (RTO) │ │ │ │◄───────────►│ │ Data Loss │ (Recovery Point │ Objective - RPO) │ Recovery Time Objective (RTO) Definition: Maximum acceptable time that a system can be down after a disaster. …

Introduction Chaos Engineering is the discipline of experimenting on a system to build confidence in the system’s capability to withstand turbulent conditions in production. Rather than waiting for failures to happen, chaos engineering proactively injects failures to identify weaknesses before they impact users. Why does this matter? In modern distributed systems (microservices, cloud infrastructure, containers), failures are inevitable. A network can partition, a server can crash, a database can slow down. Traditional testing can’t predict all the ways these components interact when things go wrong. Chaos engineering fills this gap by deliberately causing failures in a controlled way. …

Executive Summary Reliability means predictable, auditable behavior. This guide covers: Time sync: Chrony for clock accuracy (critical for logging, security) Networking: Stable interface names & hostnames (infrastructure consistency) Logging: Persistent journald + logrotate (audit trail + disk management) Shutdown: Clean hooks to prevent data loss Patching: Kernel updates with livepatch (zero-downtime), tested rollback 1. Time Synchronization (chrony) Why Time Matters Critical for: Logging: Accurate timestamps for debugging, compliance audits Security: TLS cert validation, Kerberos, API token expiry Distributed systems: Causality ordering (happens-before relationships) Monitoring: Alert timing, metric correlation Cost of poor time sync: …

Introduction Service Level Indicators (SLIs), Service Level Objectives (SLOs), and Service Level Agreements (SLAs) are fundamental concepts in Site Reliability Engineering. Understanding and implementing them correctly is crucial for maintaining reliable services. Core Concepts SLI (Service Level Indicator) Definition: A quantitative measure of service reliability from the user’s perspective. Common SLIs: Availability: Percentage of successful requests Latency: Proportion of requests served faster than threshold Throughput: Requests processed per second Error Rate: Percentage of failed requests Example SLI Definitions: …