Longhorn

TL;DR Phase 2 is the scariest phase. It’s where we take a running Jellyfin instance with years of playback history, user preferences, and media metadata — then swap the database from SQLite to PostgreSQL and restructure every volume. One wrong move and the family discovers their “Continue Watching” list is gone. This post covers deploying PostgreSQL as a k3s StatefulSet, restructuring Jellyfin’s volume layout from a monolithic RWO PVC to NFS shared config + Longhorn per-pod storage, and building a SQLite-to-PostgreSQL migration tool. ...

TL;DR A routine cluster health check surfaced seven simultaneous issues. Most were transient — Longhorn self-healed its replica fault, Prometheus recovered behind it, a stale manually-created Job was deleted in one command, and a liveness probe blip fixed itself. The real work was dnd-backend, which had been in CrashLoopBackOff and turned out to contain three separate bugs layered on top of each other. The AI identified all three during a single debugging session, authored the fixes across three PRs, and the service came up 1/1 Running with all 18 database tables created on the first boot after the final merge. ...

TL;DR Grafana went completely dark for about 26 hours on my home k3s cluster. Two things broke simultaneously: Loki entered CrashLoopBackOff, and Prometheus silently stopped ingesting metrics — its pods showed as healthy and 2/2 Running the whole time. The actual cause was Longhorn’s auto-balancer migrating replicas onto a freshly-added cluster node (k3s-agent-4) that had unstable storage during its first 48 hours. The replica I/O errors propagated directly into the workloads, corrupting mid-write files: a Prometheus WAL segment and a Loki TSDB index file. Both required offline surgery via a busybox pod to delete the corrupted files before the services could recover. ...

TL;DR Upgraded a production k3s cluster from v1.29.0+k3s1 to v1.34.4+k3s1 across 8 nodes — 3 control plane servers, 4 amd64 worker agents, and 1 arm64 Lima VM agent. The upgrade stepped through every minor version (v1.29 → v1.30 → v1.31 → v1.32 → v1.33 → v1.34) with etcd snapshots between each step. Longhorn was upgraded from v1.6.0 to v1.8.2 in two stages (v1.7.3 as an intermediate step). SSH was broken to all cluster nodes, so the entire upgrade was done via Proxmox QEMU Guest Agent (qm guest exec) and Lima CLI (limactl shell). Discovered that k3s intentionally pins Traefik to v2.11.24 even when bundling Helm chart v27 — Traefik v3 migration is a separate effort. ...

TL;DR Prometheus and Grafana both crashed with I/O errors on the same node. Before assuming software, I ran a full hardware audit across all four Proxmox hosts — SMART health, NVMe disk benchmarks (fio), CPU benchmarks (sysbench), memory bandwidth tests, and 10GbE network throughput (iperf3). The result: all hardware is healthy. The I/O errors were Longhorn CSI virtual block device corruption, not physical disk failure. Along the way, I established baseline performance numbers for every subsystem and discovered that custom cooling makes a dramatic difference in thermal performance. ...