jakman85andClaude Opus 4.8
e8c555cfeb
Greenfield spec set for a GitOps-driven PaaS+IaaS home platform: vision & requirements (R-* IDs), architecture, 14 domain specs, 11 ADRs, roadmap (phases + workstreams), and AI-agent coordination (roles, protocol, definition-of-done, task board). Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
2.2 KiB
2.2 KiB
ADR-0003 — Distributed storage: Longhorn (+ bulk tier + Velero)
- Status: Accepted
- Date: 2026-08-15
- Serves: R-STATE-01, R-STATE-02, R-STATE-03, R-STATE-04
- Supersedes: —
Context
Three nodes with local disks and no SAN must provide durable, replicated persistent storage so any workload can be destroyed and rebuilt without data loss, tolerate a single node failure, and support off-cluster backup/DR. Plex's multi-TB media library makes uniform 3× replication impractical, requiring a distinct bulk tier.
Decision
- Use Longhorn for distributed replicated block storage across the 3 nodes; default StorageClass is 3 replicas. This is the durable home for app/config state and KubeVirt VM disks (via CDI).
- Define a separate bulk media tier for large, non-replicated data (Plex library, download staging). Its concrete backing (NAS/NFS vs. dedicated large disk vs. mixed) is decided under OQ-2; Plex's metadata DB stays on 3-replica Longhorn regardless.
- Use Velero (with Longhorn backups) to push volume + resource-state backups to an off-cluster S3-compatible/NFS target on a schedule, with a tested restore path (DR drill).
Alternatives considered
- Rook/Ceph — more powerful but far heavier/operationally complex for 3 small nodes.
- OpenEBS (Mayastor/other) — viable; Longhorn chosen for simplicity, strong UI, snapshot/backup ergonomics, and fit with small clusters.
- Uniform 3× replication of everything including media — rejected: capacity-prohibitive on mini-PC local disks (R-STATE-04).
- hostPath/local-only PVs for stateful apps — rejected: node-bound, no replication, breaks the rebuild guarantee.
Consequences
- Single-node loss keeps replicated data available; workloads rebuild by re-attaching PVCs (R-STATE-01/02).
- A two-tier storage story must be clearly documented so implementers don't accidentally place bulk media on the replicated tier or app DBs on the bulk tier (04).
- Off-cluster backup target + its credentials/resilience are prerequisites (OQ-2); DR drill is part of acceptance.
- Longhorn's own capacity/health must be monitored and alerted (10).