# TrueNAS Migration Planning

## Current State

### Hardware
- CPU: AMD Ryzen 5 5600G with Radeon Graphics
- RAM: 32GB
- Network: 10GbE (mlxen0)
- Software: TrueNAS-13.0-U6.1 (Core)

### Storage Status

**hdd-pool**: 29.1TB total, **28.4TB used, 658GB free (97% capacity)** ⚠️
- mirror-0: 2x Seagate ST16000NE000 16TB HDD (16TB usable)
- mirror-1: 2x WD WD80EFBX 8TB HDD (8TB usable)
- mirror-2: 2x Seagate ST8000VN004 8TB HDD (8TB usable)

## Goal

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.

## Decisions

### Migration Approach: Option 3 - Migrate to NixOS

**Decision**: Replace TrueNAS with NixOS bare metal installation

**Rationale**:
- Aligns with existing infrastructure (16+ NixOS hosts already managed in this repo)
- Declarative configuration fits homelab philosophy
- Automatic monitoring/logging integration (Prometheus + Promtail)
- Auto-upgrades via same mechanism as other hosts
- SOPS secrets management integration
- TrueNAS-specific features (WebGUI, jails) not heavily utilized

**Service migration**:
- radarr/sonarr: Native NixOS services (`services.radarr`, `services.sonarr`)
- restic-rest: `services.restic.server`
- nzbget: NixOS service or OCI container
- NFS exports: `services.nfs.server`

### Filesystem: BTRFS RAID1

**Decision**: Migrate from ZFS to BTRFS with RAID1

**Rationale**:
- **In-kernel**: No out-of-tree module issues like ZFS
- **Flexible expansion**: Add individual disks, not required to buy pairs
- **Mixed disk sizes**: Better handling than ZFS multi-vdev approach
- **RAID level conversion**: Can convert between RAID levels in place
- Built-in checksumming, snapshots, compression (zstd)
- NixOS has good BTRFS support

**BTRFS RAID1 notes**:
- "RAID1" means 2 copies of all data
- Distributes across all available devices
- With 6+ disks, provides redundancy + capacity scaling
- RAID5/6 avoided (known issues), RAID1/10 are stable

### Hardware: Keep Existing + Add Disks

**Decision**: Retain current hardware, expand disk capacity

**Hardware to keep**:
- AMD Ryzen 5 5600G (sufficient for NAS workload)
- 32GB RAM (adequate)
- 10GbE network interface
- Chassis

**Storage architecture**:

**Bulk storage** (BTRFS RAID1 on HDDs):
- Current: 6x HDDs (2x16TB + 2x8TB + 2x8TB)
- Add: 2x new HDDs (size TBD)
- Use: Media, downloads, backups, non-critical data
- Risk tolerance: High (data mostly replaceable)

**Critical data** (small volume):
- Use 2x 240GB SSDs in mirror (BTRFS or ZFS)
- Or use 2TB NVMe for critical data
- Risk tolerance: Low (data important but small)

### Disk Purchase Decision

**Options under consideration**:

**Option A: 2x 16TB drives**
- Matches largest current drives
- Enables potential future RAID5 if desired (6x 16TB array)
- More conservative capacity increase

**Option B: 2x 20-24TB drives**
- Larger capacity headroom
- Better $/TB ratio typically
- Future-proofs better

**Initial purchase**: 2 drives (chassis has space for 2 more without modifications)

## Migration Strategy

### High-Level Plan

1. **Preparation**:
   - Purchase 2x new HDDs (16TB or 20-24TB)
   - Create NixOS configuration for new storage host
   - Set up bare metal NixOS installation

2. **Initial BTRFS pool**:
   - Install 2 new disks
   - Create BTRFS filesystem in RAID1
   - Mount and test NFS exports

3. **Data migration**:
   - Copy data from TrueNAS ZFS pool to new BTRFS pool over 10GbE
   - Verify data integrity

4. **Expand pool**:
   - As old ZFS pool is emptied, wipe drives and add to BTRFS pool
   - Pool grows incrementally: 2 → 4 → 6 → 8 disks
   - BTRFS rebalances data across new devices

5. **Service migration**:
   - Set up radarr/sonarr/nzbget/restic as NixOS services
   - Update NFS client mounts on consuming hosts

6. **Cutover**:
   - Point consumers to new NAS host
   - Decommission TrueNAS
   - Repurpose hardware or keep as spare

### Migration Advantages

- **Low risk**: New pool created independently, old data remains intact during migration
- **Incremental**: Can add old disks one at a time as space allows
- **Flexible**: BTRFS handles mixed disk sizes gracefully
- **Reversible**: Keep TrueNAS running until fully validated

## Next Steps

1. Decide on disk size (16TB vs 20-24TB)
2. Purchase disks
3. Design NixOS host configuration (`hosts/nas1/`)
4. Plan detailed migration timeline
5. Document NFS export mapping (current → new)

## Open Questions

- [ ] Final decision on disk size?
- [ ] Hostname for new NAS host? (nas1? storage1?)
- [ ] IP address allocation (keep 10.69.12.50 or new IP?)
- [ ] Timeline/maintenance window for migration?