Troubleshoot a website outage with disk full

You are on-call for a production web service. Users report the website is down (timeouts/5xx). You are told the incident turns out to involve a full disk on one or more machines.

Walk through how you would:

1. Triage and confirm impact/scope.
2. Identify the failing component(s) and the immediate cause.
3. Debug “disk full” deeply (what to check next and why).
4. Mitigate quickly and safely.
5. Prevent recurrence (monitoring, alerting, operational changes).

Assume a typical setup (load balancer → web/app tier → DB/cache; logs/metrics available). Explain what commands/signals you would look at, what hypotheses you would test, and what pitfalls you’d avoid.