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Raspberry Pi k3s fleet — Longhorn storage configuration sequence

Parent runbook: How to provision k3s, Longhorn, and Rancher on a Raspberry Pi fleet. Capture: Longhorn CSI on K3s.

Preconditions (mandatory)

  • Working k3s cluster with all nodes Ready (Bootstrap sequence).
  • open-iscsi and iscsiadm on every node that will host Longhorn replicas or components required by the docs.
  • Disks prepared per your layout (raw device, partition, or LVM LV)—follow current Longhorn documentation for disk selection and tags.

Mandatory — operator sequence (outline)

Exact commands change by Longhorn version—use the upstream install guide (Helm or manifest) you select.

  1. Install Longhorn manager, engine, and CSI driver per Longhorn-on-K3s instructions; confirm CRDs exist (kubectl get crd | grep longhorn).
  2. Confirm nodes and disks appear schedulable in the Longhorn UI or via kubectl; fix unschedulable reasons before production PVCs.
  3. Decide default StorageClass policy deliberately:
  4. P0: Often acceptable to leave Longhorn non-default until replica cost is understood.
  5. P1+: Mark default only after accepting replica CPU and IO overhead on Pis.
  6. Create a test PVC and Pod that write and read data; delete and recreate to validate binding.

Mandatory — resource realism on Raspberry Pi

Knob Guidance
Replica count Three replicas means write amplification and CPU load on small ARM cores—prefer fewer replicas for non-critical PVCs in P1.
Over-provisioning Disable or tighten if you see OOM during volume rebuilds.
Replicas on server node Some operators taint or exclude the etcd node from storage—validate against your HA plan (Hardware BOM).

Optional (HA / scale)

  • Backup target to S3-compatible or NFS storage—only after base volumes work (Backup and restore sequence).
  • Recurring snapshot/backup jobs: watch CPU during scheduled hours; prefer stable utility power on off-grid sites.

Health flow (reference)

mermaid flowchart TD I[Install Longhorn] --> D[Disks schedulable] D --> T[Test PVC] T --> P{P1+?} P -->|yes| B[Backup target + policies] P -->|no| OK[P0 complete] B --> OK2[P1 storage ready]