From Outage to Postmortem: Creating Storage Incident Runbooks

From Outage to Postmortem: Creating Storage Incident Runbooks

Hook: When a storage region or CDN goes dark, your team faces cascading failures, angry customers, and unclear bills — all while sprinting to restore service. This guide gives you template-driven runbooks, playbooks, comms templates, forensic steps and IaC examples tailored for storage and CDN failures in 2026.

Why storage- and CDN-focused runbooks matter in 2026

Cloud and edge architectures in 2026 are more distributed and dynamic than ever. Multi-cloud replication, edge caching networks, programmable CDNs, and AI-driven autoscaling reduce mean time to recovery — when you have deterministic runbooks. Recent wide-reaching incidents (for example, the Jan 2026 spike of outages affecting major CDNs and cloud providers reported across news outlets) highlight that even large providers fail; teams need playbooks that handle data availability, consistency, and client communications under pressure.

Inverted-pyramid summary: what you need now

• Immediate actions: Identify impact domain (storage vs CDN), trigger-routing to the on-call playbook, enable mitigation (failover, CDN purge throttles, origin throttling).
• Communications: Use pre-approved internal and external templates to avoid delays and errors in wording.
• Forensics: Preserve logs, create immutable snapshots, capture S3/CloudFront/Edge logs, and record API calls for postmortem. See our field guide for building a portable preservation lab to streamline on-site evidence capture.
• Postmortem: Run blameless analysis, attach timelines, RCA, action items, and SLA/SLO revisions.

Runbook template (single-page canonical format)

Use this template as a collapsed single-page canonical runbook. Host it in your runbook repository (Git) and expose a small read-only copy to your incident commander (IC) dashboard.

Runbook header

• Title: storage|cdn - [service/component] incident runbook
• Owner: team and primary on-call
• Scope: A short description of systems covered
• Severity levels: S1 (total outage), S2 (degraded), S3 (partial or internal), with SLA thresholds
• Last updated: date & commit hash

Immediate checklist (first 10 minutes)

1. Escalate to designated on-call and IC. Tag in incident channel.
2. Identify the impacted surface: origin storage (object/block/file), CDN edge, DNS, peering.
3. Collect or open live telemetry: provider status pages, CDN edge logs, origin error rates, S3 5xx trends.
4. Enable mitigations: switch traffic to failover region, enable CDN origin shield, reduce write rates if replication lag seen.
5. Post initial incident update using the external status template (see comms section).

Triage flow

1. Confirm: Are clients receiving errors (5xx/4xx), timeouts, corrupted objects, or slow reads?
2. Scope: List affected prefixes, buckets, object paths, or CDN POPs.
3. Root hypothesis: Provider outage, control-plane bug, configuration change, cache stampede, or data corruption.
4. Apply mitigation and measure effect (p50/p95/p99 latencies, error rate).

Rollback and safe-mode actions

• DNS rollback TTL guidance: set low TTLs in peacetime to enable faster failovers.
• Revert config changes via GitOps: document steps and apply via CI/CD pipeline with staged approvals.
• Open a read-only mode (static asset serving from a snapshot) if writes are compromised.

Playbooks: Storage vs CDN — actionable sequences

Playbook A — Object storage outage (S3-like providers)

1. Confirm scope: run targeted head-object and get-object tests for suspect buckets using AWS CLI/GCloud/az CLI.
2. Check provider status & incident feeds (use provider API or RSS) and correlate with internal errors.
3. If read errors only: enable multi-CDN cache cascades and origin shield; serve from nearest edge if copies exist.
4. If write errors or corruption: disable client writes, snapshot current state (versioned buckets), and initiate provider support with preserved request IDs and timestamps.
5. Run data integrity checks: compare object checksums against stored metadata (MD5/SHA256). If mismatches, isolate and preserve affected objects.
6. Failover: route traffic to replica region or warmed alternate storage (Terraform templates below to maintain warm replica).

Playbook B — CDN outages (edge POP failures, cache stampedes)

1. Identify if the outage is global or POP-level by querying multiple edges using curl with different geos or synthetic monitors.
2. Throttle origin fetches: set CDN rate-limits or origin shield to reduce origin overload and avoid origin meltdown.
3. Disable problematic edge features (compute@edge functions) if they’re triggering 5xx errors — edge compute patterns are growing fast across providers; see edge best-practices at Edge-Powered Landing Pages for examples.
4. Switch to alternate CDN provider via pre-established BGP/DNS failover or traffic steering (multi-CDN route-control).
5. Invalidate caches selectively to prevent cache stampede: use staggered TTLs and background refresh policies.

Communications templates (internal, external, and exec)

Comms must be fast, factual and repeatable. Keep templates pre-approved in your runbook repo.

Internal incident update (first message)

[INCIDENT] Impact: Storage read errors for assets under /cdn-assets/* affecting 20% of requests. Start: 2026-01-16T10:27Z. Severity: S1. Action: On-call investigating; origin throttling applied; failover to replica region initiated. Next update in 15m.

External status page template

We are investigating elevated errors affecting asset delivery for some customers. Our engineering team is applying failovers and mitigation. Impacted services: static assets and API media. Next update: in 15 minutes. We will provide an RCA within 72 hours. (We maintain an SLO of 99.99% availability; we will review credits if applicable.)

Executive summary template

Incident: S1 storage outage affecting CDN delivery. Customers impacted: ~18%. Duration: ongoing. Immediate actions: origin throttling and multi-region failover. Expected recovery: within 2 hours. Business impact: potential SLA breaches for select customers; finance alerted.

Forensics and evidence preservation

Forensic steps must be performed early. Evidence is perishable: logs rotate, caches expire, and providers may garbage-collect unreferenced objects. Preserve intelligently. For field capture best-practices, review portable preservation lab techniques and checklists.

Forensic checklist

1. Snapshot metadata: export bucket/object manifests, versions, and checksums.
2. Preserve logs: retain CDN edge logs, provider control plane logs, API audit logs, and DNS queries. Copy to immutable storage (WORM) or offline archive — consider privacy and edge-indexing patterns from privacy-first edge indexing.
3. Record API request IDs: provider support teams will ask for request IDs, timestamps, and canonical request traces.
4. Capture network traces: if possible, capture tcpdump or eBPF traces at the moment of failure for packets to/from origin and edge.
5. Isolate corrupted data: move mismatched objects to a quarantined bucket with access controls and change logs.

Forensic commands and scripts (quick starters)

Use these snippets to collect key artifacts quickly.

# Example: list latest 100 objects and checksums (AWS CLI)
aws s3api list-objects-v2 --bucket my-bucket --query 'Contents[?LastModified>=`2026-01-16`].[Key,ETag,Size]' --max-items 100

# Get CloudFront logs for a given time range (example using S3 path)
aws s3 cp s3://my-cloudfront-logs/2026/01/16/ ./logs/ --recursive --exclude "*" --include "*2026-01-16*"

# Quick health checks from multiple regions (using curl and a geo-proxy matrix)
for url in https://example.com/asset.png; do curl -s -w "\n%{http_code} %{time_total}\n" -o /dev/null $url; done

# Capture eBPF trace for disk I/O spikes (requires bpftrace)
sudo bpftrace -e 'tracepoint:block:block_rq_issue { @[comm] = count(); }'

Benchmarks and synthetic tests to include in your runbook

Automate synthetic tests that run every minute from multiple regions and feed into the runbook decision tree. Use observability playbooks and synthetic monitoring patterns described in site-search observability.

• Read benchmark: p50/p95/p99 read latency and 5xx rate using s3-bench or rclone benchmarks.
• Write benchmark: small and large object PUT latency and success rate.
• Cache-hit ratio: measure at the edge and origin.
• Cold-start test: measure first-byte times after cache invalidation to detect origin overload.

Infrastructure as Code: Terraform patterns for resilience

Keep small Terraform modules that spin up warm replicas, multi-CDN route policies, and read-only snapshots. Below is a conceptual example for creating a warm replica bucket and a CDN resource for quick switchover.

# Terraform pseudocode (conceptual)
resource "aws_s3_bucket" "primary" {
  bucket = "app-assets-primary"
  versioning { enabled = true }
}

resource "aws_s3_bucket" "replica" {
  bucket = "app-assets-replica"
  versioning { enabled = true }
  replication_configuration {
    role = aws_iam_role.replication.arn
    rules { destination { bucket = aws_s3_bucket.replica.arn } }
  }
}

# CDN resource (CloudFront / Cloudflare) with origin failover
resource "cloudfront_distribution" "cdn" {
  # origin group with primary and secondary origins
}

Maintain this IaC ready to apply with one command from a secure pipeline. Practice the failover annually and keep portable power options on your checklist (see low-budget resilience tips and the makerspace power resilience guide and field-tested power stations like the X600 Portable Power Station).

Metrics and observability: what to collect during an incident

• Traffic metrics: requests/sec by path, origin, edge POP, and client region.
• Latency distributions: p50/p95/p99 for reads and writes.
• Error rates: 4xx vs 5xx ratio, backend 502/503 counts, timeouts.
• Storage-specific: replication lag, incomplete multipart uploads, checksum mismatch counts.
• Cost signals: sudden egress spikes, repeated retries causing bill anomalies.

Postmortem template and blameless analysis

A strong postmortem turns a crisis into prevention. Use this structure:

1. Summary: one-paragraph timeline and impact.
2. Timeline: chronological minute-by-minute of detection, mitigation, and recovery. Attach logs and exact commands executed.
3. Root cause: clear technical explanation and contributing factors.
4. Why it wasn’t caught earlier: monitoring or runbook gaps.
5. Action items: assign owners, due dates, and verification steps. Prefer small, testable changes first.
6. SLA/SLO review: adjust SLOs and alert thresholds if needed; calculate customer credits if breaches occurred.

Sample postmortem action items

• Automate checksum verification on replication (Owner: Storage Eng, Due: 2 weeks)
• Deploy multi-CDN failover test suite to run monthly (Owner: SRE, Due: 1 month)
• Lower TTLs for critical DNS entries and document failover play (Owner: NetEng, Due: 1 week)

2026 trends and future-proofing your runbooks

Recent developments in late 2025 and early 2026 change our playbook recommendations:

• Edge compute proliferation: CDNs now run logic at the edge widely; runbooks must include steps to disable edge functions if they cause 5xx errors. See edge patterns and multi-origin failover approaches.
• AI Ops and automation: AI-driven incident assistants can suggest mitigations — but validate and require human approval for destructive actions. For approaches to autonomous assistants and guardrails, consult autonomous desktop AIs.
• Programmable networking: eBPF-based telemetry means richer live forensic data; include eBPF capture steps in your runbook and integrate with observability playbooks (observability & incident response).
• Multi-CDN and multi-cloud strategies: Maintain warm standbys and tested BGP/DNS failover templates (IaC) to avoid single-provider SLC (single large component) outages.
• Data governance: With stronger compliance expectations in 2026, maintain preserved audit trails for any forensic steps to avoid legal or compliance exposure. Collaborative tagging and edge-indexing approaches are useful here (privacy-first tagging).

Practical checklist to add to your first incident runbook rollout

1. Store runbooks in Git and require reviews for changes.
2. Automate a runbook health check that ensures templates, comms messages, and terraform modules are in sync.
3. Train teams via quarterly tabletop exercises and at least one live failover drill per year — consider short, focused sessions as described in the micro-meeting renaissance.
4. Instrument synthetic tests and integrate with your incident detection rules (alerts tied to SLO burn rates).
5. Keep a hunt play handy: timeline extraction script, checksum verifier, and quarantine mover.

Real-world example (short case study)

In late 2025 a mid-market SaaS provider saw a sudden spike in 503s across their app due to a CDN provider POP misconfiguration. Using a pre-authorized runbook, the SRE team: (1) throttled origin requests via the CDN API, (2) flipped traffic to a pre-warmed multi-CDN endpoint via DNS failover, and (3) published a customer-facing status page within 12 minutes. Postmortem found a mis-deployed edge worker; action items included edge feature gating and automated preflight CI checks. The incident kept SLA penalties below the threshold and reduced mean-time-to-repair by half compared to previous incidents.

Checklist: what to include in the runbook repo

• Runbook templates and per-service runbooks
• Comms templates (internal, external, exec)
• Forensic scripts and Terraform modules for failover
• Synthetic test definitions and benchmark results
• Postmortem templates and action tracker integration (issue tracker links)

Closing: actionable takeaways

• Create a single-page canonical runbook for each storage and CDN service with immediate triage and rollback steps.
• Keep comms templates pre-approved to speed external and internal messaging and reduce error-prone improvisation.
• Automate forensic captures (logs, checksums, eBPF traces) as part of the incident playbook to preserve evidence fast — see field capture best-practices in the portable preservation lab guide.
• Practice your failovers with IaC (Terraform) and maintain warm replicas for high-value datasets.
• Review SLAs/SLOs post-incident and convert postmortem actions into measurable verification steps.

Call to action: Implement this template-driven approach now: fork the runbook repo, add a storage and CDN runbook to your GitOps pipeline, and schedule a failover drill in the next 30 days. Need a starter pack (Terraform modules, comms templates, and forensic scripts) tailored for your stack? Request the Storages Cloud incident runbook starter kit and runbook audit.

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