docs: add truenas-migration plan
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docs/plans/truenas-migration.md
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docs/plans/truenas-migration.md
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# TrueNAS Migration Planning
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## Current State
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### Hardware
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- CPU: AMD Ryzen 5 5600G with Radeon Graphics
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- RAM: 32GB
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- Network: 10GbE (mlxen0)
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- Software: TrueNAS-13.0-U6.1 (Core)
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### Storage Status
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**hdd-pool**: 29.1TB total, **28.4TB used, 658GB free (97% capacity)** ⚠️
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- mirror-0: 2x Seagate ST16000NE000 16TB HDD (16TB usable)
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- mirror-1: 2x WD WD80EFBX 8TB HDD (8TB usable)
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- mirror-2: 2x Seagate ST8000VN004 8TB HDD (8TB usable)
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## Goal
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Expand storage capacity for the main hdd-pool. Since we need to add disks anyway, also evaluating whether to upgrade or replace the entire system.
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## Decisions
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### Migration Approach: Option 3 - Migrate to NixOS
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**Decision**: Replace TrueNAS with NixOS bare metal installation
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**Rationale**:
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- Aligns with existing infrastructure (16+ NixOS hosts already managed in this repo)
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- Declarative configuration fits homelab philosophy
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- Automatic monitoring/logging integration (Prometheus + Promtail)
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- Auto-upgrades via same mechanism as other hosts
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- SOPS secrets management integration
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- TrueNAS-specific features (WebGUI, jails) not heavily utilized
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**Service migration**:
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- radarr/sonarr: Native NixOS services (`services.radarr`, `services.sonarr`)
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- restic-rest: `services.restic.server`
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- nzbget: NixOS service or OCI container
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- NFS exports: `services.nfs.server`
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### Filesystem: BTRFS RAID1
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**Decision**: Migrate from ZFS to BTRFS with RAID1
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**Rationale**:
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- **In-kernel**: No out-of-tree module issues like ZFS
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- **Flexible expansion**: Add individual disks, not required to buy pairs
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- **Mixed disk sizes**: Better handling than ZFS multi-vdev approach
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- **RAID level conversion**: Can convert between RAID levels in place
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- Built-in checksumming, snapshots, compression (zstd)
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- NixOS has good BTRFS support
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**BTRFS RAID1 notes**:
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- "RAID1" means 2 copies of all data
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- Distributes across all available devices
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- With 6+ disks, provides redundancy + capacity scaling
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- RAID5/6 avoided (known issues), RAID1/10 are stable
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### Hardware: Keep Existing + Add Disks
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**Decision**: Retain current hardware, expand disk capacity
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**Hardware to keep**:
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- AMD Ryzen 5 5600G (sufficient for NAS workload)
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- 32GB RAM (adequate)
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- 10GbE network interface
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- Chassis
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**Storage architecture**:
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**Bulk storage** (BTRFS RAID1 on HDDs):
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- Current: 6x HDDs (2x16TB + 2x8TB + 2x8TB)
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- Add: 2x new HDDs (size TBD)
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- Use: Media, downloads, backups, non-critical data
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- Risk tolerance: High (data mostly replaceable)
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**Critical data** (small volume):
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- Use 2x 240GB SSDs in mirror (BTRFS or ZFS)
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- Or use 2TB NVMe for critical data
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- Risk tolerance: Low (data important but small)
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### Disk Purchase Decision
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**Options under consideration**:
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**Option A: 2x 16TB drives**
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- Matches largest current drives
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- Enables potential future RAID5 if desired (6x 16TB array)
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- More conservative capacity increase
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**Option B: 2x 20-24TB drives**
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- Larger capacity headroom
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- Better $/TB ratio typically
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- Future-proofs better
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**Initial purchase**: 2 drives (chassis has space for 2 more without modifications)
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## Migration Strategy
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### High-Level Plan
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1. **Preparation**:
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- Purchase 2x new HDDs (16TB or 20-24TB)
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- Create NixOS configuration for new storage host
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- Set up bare metal NixOS installation
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2. **Initial BTRFS pool**:
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- Install 2 new disks
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- Create BTRFS filesystem in RAID1
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- Mount and test NFS exports
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3. **Data migration**:
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- Copy data from TrueNAS ZFS pool to new BTRFS pool over 10GbE
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- Verify data integrity
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4. **Expand pool**:
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- As old ZFS pool is emptied, wipe drives and add to BTRFS pool
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- Pool grows incrementally: 2 → 4 → 6 → 8 disks
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- BTRFS rebalances data across new devices
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5. **Service migration**:
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- Set up radarr/sonarr/nzbget/restic as NixOS services
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- Update NFS client mounts on consuming hosts
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6. **Cutover**:
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- Point consumers to new NAS host
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- Decommission TrueNAS
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- Repurpose hardware or keep as spare
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### Migration Advantages
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- **Low risk**: New pool created independently, old data remains intact during migration
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- **Incremental**: Can add old disks one at a time as space allows
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- **Flexible**: BTRFS handles mixed disk sizes gracefully
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- **Reversible**: Keep TrueNAS running until fully validated
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## Next Steps
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1. Decide on disk size (16TB vs 20-24TB)
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2. Purchase disks
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3. Design NixOS host configuration (`hosts/nas1/`)
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4. Plan detailed migration timeline
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5. Document NFS export mapping (current → new)
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## Open Questions
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- [ ] Final decision on disk size?
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- [ ] Hostname for new NAS host? (nas1? storage1?)
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- [ ] IP address allocation (keep 10.69.12.50 or new IP?)
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- [ ] Timeline/maintenance window for migration?
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