Ubuntu 16.04 LTS high load average caused by I/O wait saturation

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Users experience latency spikes while system load climbs despite moderate CPU utilization.

Environment & Reproduction

Often appears during backup windows, log storms, or noisy-neighbor storage contention.

Root Cause Analysis

Processes block on slow disk operations and queue depth grows beyond service tolerance.

Quick Triage

Measure iowait and per-device throughput to isolate hottest disks and workloads.

Step-by-Step Diagnosis

Use iostat and pid-level tracing to map heavy writes and sync behavior.

Solution – Primary Fix

Throttle offending jobs, tune flush intervals, and relocate high-write paths to faster volumes.

Solution – Alternative Approaches

Scale out storage tier, enable caching, or shift non-critical batch jobs off-peak.

Verification & Acceptance Criteria

Load and latency stabilize with iowait back within baseline SLO ranges.

Rollback Plan

Revert scheduler and throttling changes if throughput regression impacts business tasks.

Prevention & Hardening

Implement I/O observability, queue-depth alerts, and workload isolation policies.

Related Errors & Cross-Refs

Blocked process warnings, ext4 commit delays, and timeout errors in dependent services.

Related tutorial: View the step-by-step tutorial for Ubuntu 16.04 LTS.

View all Ubuntu 16.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu and Linux performance tuning guides for I/O constrained systems.