TrueNAS vs Unraid: Which NAS OS?

Quick Verdict

TrueNAS SCALE for data integrity. Unraid for flexibility.

TrueNAS uses ZFS — the gold standard for data integrity. If your NAS stores irreplaceable data (photos, documents, backups), ZFS’s checksums and self-healing are unmatched. But ZFS is rigid — you can’t add a single drive to an existing RAID-Z vdev.

Unraid lets you mix any size drives and add storage incrementally. GPU passthrough and Community Applications make it the better Docker platform. But its parity system offers less data protection than ZFS.

Choose TrueNAS if data integrity is your top priority and you’ll buy drives in matching sets. Choose Unraid if you want maximum flexibility and will accumulate drives over time.

Feature Comparison

Feature	TrueNAS SCALE	Unraid
Price	Free (open source)	$59-129 (one-time)
File system	ZFS	XFS/Btrfs per drive
Data integrity	ZFS checksums + self-healing	Parity check (no checksums on data)
RAID	RAID-Z1/Z2/Z3, Mirror	1 or 2 parity drives
Mixed drive sizes	Within a vdev: no. New vdevs: yes	Full support
Add drives	New vdev only (can’t expand existing RAID-Z)	Any drive, any time
Compression	ZFS LZ4 (transparent, 1.5-2x savings)	Per-drive Btrfs only
Snapshots	Native ZFS (instant, space-efficient)	Btrfs snapshots (if using Btrfs)
Docker	Native Docker Compose + Apps catalog	Docker + Community Applications (700+)
VMs	KVM/QEMU	KVM with GPU passthrough
GPU passthrough	Supported (requires config)	Native support in web UI
Web UI	Good (improved in recent versions)	Good (functional)
Boot media	Dedicated SSD/USB	USB flash drive only
Cache/SLOG	ZFS SLOG + L2ARC (NVMe)	Cache pool (NVMe, write-back)
Replication	ZFS send/receive (incremental, encrypted)	Community plugins
RAM usage	Heavy (ZFS ARC: 1 GB base + 1 GB/TB recommended)	Light (~2-4 GB for OS)
ECC RAM	Recommended (not required)	Not needed
Community	r/truenas, forums	r/unraid, forums

Data Integrity: ZFS vs Parity

TrueNAS (ZFS)

ZFS checksums every block of data. On every read, it verifies the checksum. If a block is corrupted (bit rot, firmware bug, cosmic ray), ZFS detects it. With redundancy (mirror or RAID-Z), ZFS automatically replaces the corrupt block with the good copy. Silent data corruption is impossible with ZFS.

Scheduled scrubs verify every block on disk — even data that hasn’t been read recently. This catches bit rot before it becomes a problem.

ZFS snapshots are instantaneous, space-efficient, and can be sent to a remote TrueNAS system for off-site backup.

Unraid (Parity)

Unraid’s parity system protects against drive failure — if a drive dies, parity data on the parity drive(s) can reconstruct it. But Unraid does not checksum individual data blocks. If a file on a data drive gets silently corrupted (bit rot), Unraid won’t detect it. The parity data actually gets updated to match the corrupted data on the next parity sync.

The practical impact: For media files (movies, music) that are written once and rarely changed, bit rot risk is low. For databases, documents, and photos, ZFS’s checksums are a meaningful safety advantage.

Storage Flexibility

TrueNAS ZFS Constraints

A vdev cannot be expanded. A 3-drive RAID-Z1 vdev stays 3 drives. To add storage, you add a new vdev (another set of drives).
All drives in a vdev should match. Different sizes work, but usable space per drive equals the smallest drive.
Planning required. Decide your vdev layout upfront. Changing it means destroying and recreating the pool.

Example growth path on TrueNAS:

Start with 3x 8 TB in RAID-Z1 = 16 TB usable
Want more space? Add another vdev: 3x 8 TB RAID-Z1 = 32 TB usable total
Can’t just add a single 16 TB drive to the existing vdev

Unraid Flexibility

Add any drive at any time. Buy a drive, plug it in, assign to array.
Mixed sizes are native. 4 TB, 8 TB, 16 TB — all in one array.
Parity drive must be ≥ largest data drive. Plan this accordingly.
Remove drives by moving data to other drives.

Example growth path on Unraid:

Start with 1x 8 TB parity + 1x 4 TB data = 4 TB usable
Add 1x 8 TB data = 12 TB usable
Add 1x 16 TB data + upgrade parity to 16 TB = 28 TB usable

No RAID rebuilds. No vdev constraints. Just add drives.

Docker and Self-Hosting

TrueNAS SCALE

Native Docker Compose via CLI (SSH in and use standard Docker)
TrueNAS Apps catalog (curated, one-click installs)
TrueCharts (community catalog — 500+ apps, but has had stability/governance issues)
Dataset-based storage for Docker volumes
GPU passthrough supported (requires CLI configuration)

Pain points:

TrueNAS Apps UI has improved but can be confusing
TrueCharts catalog has had availability issues — many users now use plain Docker Compose
Docker volume paths with ZFS datasets can be unintuitive
Major version upgrades have broken app configurations in the past

Unraid

Docker built into the web UI with template support
Community Applications (CA) — 700+ templates with one-click install
Templates pre-configure ports, volumes, and environment variables
GPU passthrough natively supported via web UI
Straightforward Docker management — feels natural

Pain points:

Some CA templates are outdated or poorly maintained
Docker storage is on the cache drive by default — understand this before filling your cache
Updates to Docker host can occasionally break containers

Winner for Docker: Unraid. Community Applications’ template system and native GPU passthrough in the UI make it more accessible for self-hosting than TrueNAS’s Docker implementation.

Performance

Read Speed

TrueNAS (RAID-Z): Reads stripe across all drives in a vdev. A 4-drive RAID-Z1 can deliver 500+ MB/s sequential reads. ZFS ARC cache serves hot data at RAM speed.
Unraid: Each file lives on one drive. Read speed = single drive speed (~180-200 MB/s for HDD). No striping benefit.

TrueNAS is significantly faster for reads, especially for large files and multi-user access.

Write Speed

TrueNAS (RAID-Z): Writes are distributed across vdev drives with parity. 200-400 MB/s typical. SLOG (NVMe) can buffer sync writes for database workloads.
Unraid: Array writes are single-drive speed (~150 MB/s for HDD). Cache pool (NVMe) absorbs writes first, then mover transfers to array in background. Effective speed feels fast for normal use.

TrueNAS is faster for sustained large writes. Unraid’s cache pool makes normal use feel fast, but large transfers (multiple TB) are bottlenecked by single-drive array writes.

RAM Efficiency

TrueNAS: ZFS ARC cache aggressively uses available RAM. With 32 GB, ~24 GB becomes ARC cache — frequently accessed data is served at RAM speed. This makes TrueNAS exceptionally responsive for repeated file access patterns.
Unraid: Uses 2-4 GB for the OS. Remaining RAM is available for Docker containers and VMs. No equivalent to ZFS ARC.

Pricing

Both are free or cheap for the software — the cost is in hardware.

Configuration	TrueNAS	Unraid
Software	Free	$59-129
Minimum RAM	16 GB recommended (for ZFS ARC)	8 GB sufficient
ECC RAM	Recommended (+$30-50 premium)	Not needed
Boot drive	16+ GB SSD	USB flash drive ($10)
Total for same hardware	Free + hardware	$59-129 + hardware

Unraid’s license cost is offset by lower RAM requirements. TrueNAS’s “free” software comes with a recommendation for 16-32 GB RAM (vs 8 GB for Unraid), which adds $30-60 to the hardware cost.

Choose TrueNAS If…

Data integrity is paramount. ZFS checksums and self-healing are unmatched.
You want ZFS features. Compression, snapshots, replication, scrubs.
You’ll buy drives in matching sets. 3-4 matching drives at a time, not incrementally.
You have RAM to spare. 16-32 GB for optimal ZFS ARC cache.
You want free software. No license cost.
You need efficient off-site backup. ZFS send/receive is the best replication solution available.

Choose Unraid If…

You want to add drives one at a time. Mixed sizes, incremental growth.
You want GPU passthrough. For Plex transcoding, Jellyfin, AI workloads.
Community Applications appeal to you. 700+ one-click Docker templates.
You want VMs with dedicated resources. Unraid’s VM management is more polished.
You’re building a media server. Unraid’s flexibility + GPU passthrough = ideal Plex/Jellyfin setup.
You have limited RAM. 8 GB is enough for Unraid.

Final Verdict

TrueNAS is the better NAS. ZFS is objectively superior for data integrity, performance, and features like compression and replication.

Unraid is the better home server. GPU passthrough, flexible storage, and Community Applications make it the better platform for self-hosting Docker containers and VMs alongside storage.

If you primarily want storage with some Docker: TrueNAS. If you primarily want a Docker/VM server with flexible storage: Unraid. Many homelabbers run both — TrueNAS for critical data, Unraid or a mini PC for containers.

FAQ

Can I migrate from Unraid to TrueNAS (or vice versa)?

Not directly — the file systems are incompatible. You’ll need to back up all data to external storage, install the new OS, create a new array/pool, and restore. Plan for this to take hours to days depending on data volume.

Does TrueNAS SCALE support Unraid-style mixed drives?

No. ZFS vdevs require matching drives. You can add different-sized vdevs to a pool, but within each vdev, drives should match.

Is ZFS worth the complexity?

For irreplaceable data (photos, documents, legal/financial records), absolutely. For media that can be re-downloaded, the integrity advantage is less critical. ZFS’s compression alone can save 30-50% of storage space for compressible data.

Can Unraid use ZFS?

Unraid 7.x added ZFS support for cache pools. The main array still uses Unraid’s traditional parity system. It’s not a full ZFS implementation like TrueNAS.