nixos-servers/docs/plans/truenas-migration.md

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?