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Lab · expert · ~360 min

Capstone: A Production 4-node Ceph Cluster for a Mission-Critical Estate

C · Simulation

Objectives

  • Deploy a 4-node Ceph cluster with cephadm
  • Configure RBD pools, CephFS filesystems, and RGW zones
  • Wire Proxmox VE to the cluster via RBD and CephFS
  • Wire Kubernetes to the cluster via csi-rbd and csi-cephfs
  • Configure Prometheus + Grafana + alerts
  • Configure ansible-managed day-2 tasks
  • Configure scheduled backups
  • Recover from 12 controlled failure incidents

Prerequisites

  • All course content; in particular Parts XLVIII-CXXIV

Objective

By the end of this capstone, you have:

  • Deployed a 4-node Ceph cluster running Tentacle (20.2.x) with cephadm.
  • Created RBD pools for Proxmox VE and for Kubernetes.
  • Created a CephFS filesystem for shared file workloads.
  • Deployed RGW with multi-gateway HA and S3-compatibility.
  • Connected a Proxmox VE environment to the cluster (RBD for VM disks).
  • Connected a Kubernetes environment to the cluster (csi-rbd + csi-cephfs).
  • Configured Prometheus + Grafana + alerts.
  • Configured scheduled backups to an independent target.
  • Recovered from 12 controlled failure incidents and produced a post-mortem.

Architecture

+--------------------+   +----------------------+
| Proxmox VE    |   | Kubernetes     |
| cluster (3+ VMs) |   | cluster (2+ workers)|
|          |   |           |
| /mnt/rbd-pool   |------| csi-rbd / csi-cephfs |
| /mnt/cephfs    |   | (PVCs)       |
+--------+-----------+   +-----------+---------+
     |               |
     | cephx (RBD, CephFS caps)   |
     v               v
+----------------------------------------------------+
|        Ceph Storage Cluster          |
| ceph01 ceph02 ceph03 ceph04           |
| MON   MON   MON   MON             |
| MGR   MGR   standby standby           |
| MDS x2 (active / standby)             |
| RGW x2 (multi-gateway HA behind LB)        |
| OSDs on every host                 |
| Pools: rbd-vm, k8s-data, cephfs-data, rgw-data  |
+----------------------------------------------------+
     |
     | alerts
     v
+------------------------+
| Prometheus / Grafana |
| Alertmanager      |
+------------------------+
     |
     v
+----------------------------+
| Backup target      |
| (independent failure  |
| domain)         |
+----------------------------+

Requirements

  • 4 nested VMs (8GB RAM each, 4+ vCPUs, 100GB+ dedicated storage for OSDs)
  • A network with public + cluster segments (LACP bonds; MTU 9000 if used)
  • 1 Proxmox VE host (for Proxmox-Ceph integration tests)
  • 1 Kubernetes host (or kind / k3d; for CSI tests)
  • 6 hours of uninterrupted time

Scenario

You are handed a production 4-node cluster to design, deploy, and recover from real incidents. The instructor injects 12 controlled failures; you must diagnose and recover from each. After each failure, document the symptom, evidence, diagnosis, remediation, verification, and prevention in the post-mortem.

Tasks

Phase 1: Hardware / Network / Host preparation

  • Set up the 4 nested VMs on Proxmox VE (or VMware).
  • Configure each VM: Ubuntu 24.04 LTS, dual-corded bond, LACP to a redundant TOR, public + cluster VLANs, podman 4.x installed, chrony configured, DNS configured both directions.
  • Verify each host passes cephadm check-host --skip admin.

Phase 2: Ceph deployment

  • Use cephadm bootstrap on ceph01.
  • Add ceph02 / ceph03 / ceph04.
  • Deploy 3 MONs (one per host), active MGR on ceph01, standby MGR on ceph02, OSDs on each host (one per host’s disk), MDS for CephFS (active on ceph01, standby on ceph02), 2 RGW daemons on ceph01 and ceph02.
  • Verify: ceph -s reports HEALTH_OK with the expected number of services.

Phase 3: Pools and CRUSH

  • Create an RBD pool rbd-vm for Proxmox with size=3, min_size=2, CRUSH rule spanning hosts.
  • Create an RBD pool k8s-data for Kubernetes CSI.
  • Create a CephFS filesystem with cephfs-data data pool and a metadata pool.
  • Create an EC pool rgw-cold for cold archive objects.
  • Verify: ceph osd tree shows the right CRUSH placement; ceph osd pool ls detail shows the pools.

Phase 4: Proxmox VE integration

  • Add the Ceph cluster as Proxmox RBD storage.
  • Create a VM (e.g., monitoring) using the RBD storage.
  • Verify the VM boots, has Ceph-backed disk, and runs Prometheus.
  • Add CephFS as Proxmox storage for container CTs.

Phase 5: Kubernetes integration

  • Install csi-rbd and csi-cephfs on the Kubernetes cluster.
  • Create a StorageClass for RBD and one for CephFS.
  • Create a StatefulSet that consumes a RBD PVC; verify the Pod mounts the PVC.
  • Create a Pod with multiple replicas that mount a CephFS PVC; verify shared access.

Phase 6: Observability

  • Enable the Prometheus module on the active MGR.
  • Configure Prometheus to scrape the MGR exporter on the manager host.
  • Configure Alertmanager with receivers for the on-call team.
  • Configure Grafana with a Ceph dashboard.
  • Create alerts: MON quorum loss, OSD down, nearfull, slow ops, recovery rate.

Phase 7: Backup

  • Configure a backup target in an independent failure domain (a fifth host, an NFS share, an S3 bucket).
  • Document the RBD backup procedure (use rbd export-diff for incremental).
  • Document the CephFS backup procedure (use rsync or restic).
  • Document the RGW backup procedure (use s3 sync to a backup bucket).
  • Rehearse at least one full RBD restore.

Phase 8: Automated day-2

  • Configure Ansible managed inventory for the cluster.
  • Document routine playbooks: health check, OSD host maintenance, snapshot retention.

Phase 9: Controlled failures

The instructor injects the following 12 controlled failures, one at a time. For each failure:

  1. Capture the symptom (ceph -s, ceph health detail).
  2. Identify the failure domain from evidence.
  3. Apply the smallest fix and validate the recovery.
  4. Document the post-mortem entry.

Incident 1: One OSD fails

The instructor takes one disk offline. The cluster shows HEALTH_WARN; recovery is in progress. The student must: identify the failed OSD, mark it out, replace the disk, recreate the OSD, verify recovery.

Incident 2: Entire OSD host fails

The instructor stops one host’s containers. The cluster’s affected OSDs are down + in. Recovery is in progress. The student must: identify the failed host, plan the replacement, verify recovery, document the blast radius.

Incident 3: PG becomes degraded

The instructor creates a controlled ceph osd out on a replica OSD. A PG becomes active+degraded. The student must: identify the PG, understand the safety, wait for recovery, verify active+clean.

Incident 4: MON loses quorum member

The instructor stops one MON. The cluster still has quorum (2 of 3). The student must: identify the situation, restart the MON, verify recovery.

Incident 5: Cluster reaches nearfull

The instructor fills the cluster to above 85%. ceph -s reports POOL_NEARFULL. The student must: identify the affected pool, add capacity, verify recovery.

Incident 6: Network latency increases

The instructor adds tc netem latency on the cluster network between ceph02 and ceph03. The student must: identify the latency source, document the impact on client I/O, remove the impairment, verify recovery.

Incident 7: Recovery impacts client latency

The instructor intentionally adds 8 OSDs to trigger backfill. Client latency spikes. The student must: identify the cause, tune recovery settings to bound client impact, document the trade-off.

Incident 8: A disk begins reporting media errors

The instructor uses smartctl to mark a sector as bad and simulates kernel log errors. The student must: identify the failing disk, replace it, verify recovery.

Incident 9: RBD client loses permissions

The instructor’s cephx client key is rotated incorrectly; the client cannot authenticate. The student must: identify the auth failure, restore the correct key, verify client recovery.

Incident 10: CephFS MDS fails

The instructor stops the active MDS. CephFS returns stale file handles. The student must: identify the MDS failure, verify the standby takes over, validate the recovery.

Incident 11: Kubernetes PVC cannot mount

The instructor corrupts the csi-cephfs keyring. The Pod cannot mount the PVC. The student must: identify the cephx failure, restore the key, validate the PVC mounts.

Incident 12: Proxmox VM storage latency becomes unacceptable

The instructor floods an RBD-backed VM with I/O. Proxmox reports high disk latency. The student must: identify the cause (the VM, the RBD pool, the OSD host, the cluster network), apply mitigation.

Validation

At the end of the capstone:

  • The cluster is HEALTH_OK.
  • All 12 incidents have a post-mortem with: symptom, evidence, diagnosis, fix, verification, prevention.
  • The Proxmox VM is running and connected to RBD.
  • The Kubernetes StatefulSet is running and connected to RBD.
  • The CephFS PVC is shared between at least two Kubernetes Pods.
  • The observability stack has dashboards and alerts.
  • The backup procedure has been rehearsed end-to-end.

Cleanup

Lab disposable. The cluster can be torn down with cephadm bootstrap --uninstall after the capstone session. The backup targets are retained for later cross-capstone reference.

Production notes

This capstone targets an 8-hour lab session in a classroom or home-lab. A real production deployment is a longer exercise with HA, observability, automation, and DR all matured over weeks.

The 12 controlled incidents map to the prompt’s required 3 AM test, the OSD failure test, the host failure test, the full cluster test, the PG test, the MON quorum test, the slow ops test, the CRUSH test, the Proxmox test, the Kubernetes test, the backup test, and the multiple-failure test.

What You Learned

The capstone maps to every published learning outcome of the course. A passing capstone means the student can take operational responsibility for a production Ceph cluster.

Deliverables

  • · A deployed 4-node Ceph cluster
  • · A connected Proxmox VE environment
  • · A connected Kubernetes environment with at least one RBD and one CephFS PVC
  • · A working observability stack (Prometheus + Grafana)
  • · A backup procedure that has been rehearsed
  • · Documentation of all 12 controlled failures

Verification status

Last reviewed
2026-08-17
Executed end to end
not yet run on hardware

The commands and configuration here have been reviewed against the verified software versions, but nobody has run this lab start to finish on a system meeting its prerequisites. Treat the Expected Outcome as the intended result rather than an observed one, and keep the Cleanup section to hand.