Unraid vs Synology (and TrueNAS): Which NAS to Buy

Unraid or TrueNAS: choose Unraid if you will add mismatched drives one at a time and mostly store media, because each disk keeps its own filesystem behind up to two parity drives. Choose TrueNAS (the project formerly called FreeNAS) for free, checksummed ZFS on matched disks. Choose Synology if you want a supported appliance instead of a build.

The three are different bets about how storage grows and what happens when a disk dies. Comparing them on features misses the point; comparing them on expansion and failure behaviour makes the decision almost mechanical. Versions below are the current stable releases in October 2026: Unraid 7.3.3, TrueNAS Community Edition 25.10.7 and Synology DSM 7.4.

The three storage models in one paragraph each

Unraid gives every array disk its own independent filesystem and writes each file whole onto one disk. A separate parity disk holds computed parity across the others, which is what allows a failed disk to be rebuilt. Because nothing is striped, disks of different sizes coexist and a single disk can be added at any time. The mechanism, and what it costs, is covered in how Unraid storage works. ZFS and BTRFS pools sit alongside the array, and since Unraid 7.0 the array itself is optional.

TrueNAS is a ZFS appliance operating system, built on Debian Linux in its current Community Edition. Data is striped across all disks in a RAIDZ group with distributed parity. OpenZFS documents raidz1, raidz2 and raidz3 as tolerating one, two and three device failures respectively, with a minimum group size one larger than the parity count and a recommended group size of three to nine disks. Every block is checksummed, so silent corruption is detected rather than propagated.

Synology DSM is a turnkey appliance: sealed hardware, vendor operating system, Btrfs or ext4 on internal drives, and a support relationship. The DS225+ is the current small two-bay model, rated by Synology for up to 40 TB raw with 20 TB drives and quoting over 282 MB/s sequential read and 217 MB/s sequential write from its own internal testing over its built-in 2.5 gigabit port.

Side by side

Unraid vs TrueNAS: which should you run?

Run Unraid when the drives are a mix of sizes bought over years, the server is mainly media plus Docker apps, and you want to add one disk at a time from the web UI. Run TrueNAS when every block must be checksummed, snapshots and replication are part of the plan, and paying nothing for the OS matters.

The gap is narrower than reviews from the FreeNAS era suggest, because each has adopted the other’s strengths:

• Unraid runs ZFS. Unraid 6.12 added ZFS pools in June 2023, 7.0 made the parity array optional, and 7.2 added RAIDZ expansion to the web interface. Unraid 7.3.3 ships ZFS 2.4.4.
• TrueNAS runs Docker. TrueNAS 24.10, released 29 October 2024, replaced its Kubernetes apps back-end with Docker Compose and added online RAIDZ expansion one drive at a time.
• Both virtualise with KVM. Unraid’s VM stack is KVM, QEMU, libvirt and VFIO passthrough; TrueNAS 25.10 also runs its virtual machines on KVM.

What still separates them:

• The array. TrueNAS has only ZFS pools. Unraid’s parity array of independent, mixed-size disks has no TrueNAS equivalent.
• Price. TrueNAS Community Edition is free and open source. Unraid costs $49 (Starter, six devices), $109 (Unleashed) or $249 (Lifetime) on Unraid’s store, checked October 2026. Starter and Unleashed include a year of updates, then an optional $36 a year; the licensing FAQ says a lapsed licence keeps running its current version. The array caps at 30 devices, 28 data and 2 parity.
• Hardware floor. The TrueNAS hardware guide asks for 8 GB of RAM and a 20 GB SSD boot device, says USB sticks typically cannot handle TrueNAS’s boot-pool writes, and notes that most users strongly recommend ECC memory. Unraid boots from a USB flash drive, and 7.3.0 added booting from an internal drive.
• Apps. Unraid’s Community Applications catalogue lists over 2,000 free containers and plugins as ready-made templates; how to set up Unraid Docker containers walks through it.

If virtual machines matter more than storage, the closer contest is Unraid vs Proxmox.

FreeNAS, TrueNAS SCALE and Community Edition

“Unraid vs FreeNAS” and “Unraid vs TrueNAS SCALE” are the same comparison under older names. iXsystems made TrueNAS 12.0 CORE the upgrade path for FreeNAS 11.3 in October 2020 and released the Debian-based SCALE in 2022. With 25.04 “Fangtooth” on 15 April 2025, SCALE was renamed TrueNAS Community Edition, and the FreeBSD-based CORE was left in maintenance; Wikipedia’s TrueNAS entry records its final release as 13.3-U1.2 on 29 April 2025. A FreeNAS-era review is describing that retired FreeBSD branch. For a three-way that adds OpenMediaVault, see TrueNAS SCALE vs Unraid vs OMV.

Unraid vs Synology: drives, hardware and price

Unraid wins on drive choice and room to grow; Synology wins on time to a working NAS. Drives became the sharper issue in 2025. The DSM 7.3 release on 8 October 2025 extended third-party drive support on 2025 DiskStation Plus, Value and J Series units from migration only to installation and storage pool creation, but M.2 storage pools and cache still need drives from Synology’s compatibility list. DSM 7.4, released 16 June 2026, added deduplication and compression for hard-drive volumes, and Synology hard drives are required to use it. Unraid and TrueNAS keep no such list.

The DS225+ itself has two bays, an Intel Celeron J4125, 2 GB of DDR4 expandable to 6 GB, and one 1GbE plus one 2.5GbE port. How-To Geek’s June 2026 review priced it at $340 without drives; in October 2026 the Newegg listing showed Adorama selling it at $364.99. Two bays is also its ceiling. The comparable Unraid outlay is a $49 Starter licence for six devices plus hardware, and if drives are the main expense, best hard drives for Unraid covers which CMR models are worth buying.

TrueNAS vs Synology: which is better?

Synology is better if you want a small appliance with vendor support, SHR for mixed drive sizes and an OS that runs in 2 GB of RAM. TrueNAS is better if you are building your own server and want ZFS checksums, free software and any drive you like, at the cost of an 8 GB RAM floor.

Both detect bit rot, in different places. ZFS checksums every block in every pool, while DSM’s checksums and snapshots come from Btrfs, one of two internal file systems in the DSM 7.3 specifications alongside ext4, so pick Btrfs when creating the volume. The same specifications cap a single volume at 200 TiB, or 1 PiB as a Btrfs peta volume.

Apps and VMs are closer than the price gap suggests. DSM’s Container Manager runs multi-container Docker Compose projects, and Virtual Machine Manager is rated for two VM instances on the DS225+; TrueNAS runs Docker apps and KVM guests. The real difference is headroom: the DS225+ takes 6 GB of memory at most, less than TrueNAS’s 8 GB starting point. “DSM vs TrueNAS” is therefore appliance versus build, since DSM comes with Synology hardware and TrueNAS Community Edition installs on any x86_64 machine.

Expansion is the decisive difference

This is where most of the regret lives, so it is worth being precise about each one.

Unraid adds a single disk of any size to an existing array from the web interface, provided the licence has a free device slot and the new disk is no larger than the smallest parity disk. There is no re-layout and no rewrite of existing data.

ZFS is stricter. A raidz vdev can now be widened by attaching a device, but blocks written before the expansion keep their original data-to-parity ratio, so the traditional approach of adding a whole new vdev at a time, and buying disks in matched groups, still applies. Unraid’s ZFS pools follow the same rules: Unraid 7.2 added web-interface RAIDZ expansion for single-vdev pools, one drive at least as large as the pool’s smallest at a time, while Unraid’s ZFS documentation still describes growth as adding a vdev of the same layout. For this decision the shape is what matters, not the detail: ZFS grows in planned groups while Unraid grows one disk at a time.

Synology sits between the two. Synology Hybrid RAID absorbs mixed drive sizes, but the ceiling is the bay count of the chassis you bought, and adding bays means an expansion unit or a new appliance.

If the growth pattern is “one drive whenever a good deal appears”, Unraid is the only one of the three that matches it without penalty.

Failure behaviour is the second difference

Redundancy levels are comparable. What differs is what a failure beyond the redundancy level actually costs.

Because Unraid does not stripe, a loss that exceeds parity costs the contents of the failed disks only. Every surviving disk still holds a complete, mountable filesystem that can be read on any Linux machine. In a striped RAIDZ pool, losing more devices than the parity level loses the pool, because every file is spread across every disk in the vdev. The same is true of a conventional RAID volume in an appliance.

That asymmetry is the strongest single argument for Unraid on a bulk media array, where the data is large, replaceable in principle, and not worth the cost of a second full copy. It is the weakest argument on data you cannot lose, where the right answer is an off-machine backup regardless of which of the three you run.

Performance, honestly

Unraid reads a single file from a single disk, so single-stream throughput is one disk’s throughput no matter how many disks are in the array. Writes to the array are slower still because of the parity read-modify-write cycle, which is why a cache pool exists.

ZFS is the opposite shape. Streaming bandwidth scales with the number of data disks in a vdev, but OpenZFS is careful to note that with the default 128 KiB record size a block spans every data column, so random-read IOPS works out roughly the same as a single disk however wide the group. The “RAIDZ gives you the IOPS of one disk” rule of thumb is about that default configuration rather than a property of RAIDZ itself, and mirrors remain the better choice when random-read IOPS is the binding constraint.

For a media server, several simultaneous streams from different disks is the workload that matters, and all three handle it. For a virtual machine datastore, none of the parity layouts is the right answer; a mirrored solid-state pool is.

Memory and hardware expectations

The claim that ZFS needs 1 GB of RAM per TB of storage is repeated constantly and Unraid’s documentation calls it a myth outright. ZFS uses RAM for its adaptive replacement cache, and Unraid caps that cache at roughly one eighth of system memory so it cannot starve containers and virtual machines; since 7.3.0 that ceiling is adjustable as zfs_arc_max under Settings, Disk Settings. Size RAM for the workload running on top of the storage, not for the pool size.

Synology removes the hardware question entirely, which is the point of buying one, but it also constrains it: the DS225+ product page directs buyers to Synology’s drive compatibility list before purchasing drives. On a self-built Unraid or TrueNAS box, any drive that reports SMART data is a candidate. Sizing a self-built machine is covered in the Unraid hardware guide.

Which one to buy

Choose Unraid if the array will grow one disk at a time, the drives are a mix of sizes and ages, the bulk of the data is media, and the failure mode that matters is “lose one disk’s worth” rather than “lose everything”. Budget for the licence tier that covers every attached device, including cache SSDs.

Choose TrueNAS if the data is small enough to buy disks in matched groups, snapshots and end-to-end checksums are the point, and replication to a second machine is part of the plan. It is also the better answer when a single dataset needs more sequential throughput than one disk can provide.

Choose Synology if the goal is for storage to stop being a project. The trade is flexibility and drive choice for a supported appliance that a household member can also administer. The DS225+ is the current two-bay model; the older Synology DS223 remains the cheaper two-bay option, and the single-bay Synology DS124 suits a pure backup target where redundancy comes from having a second copy elsewhere.

Whichever way the decision goes, redundancy is not backup in any of the three. Parity, RAIDZ and SHR all protect against a disk dying and none of them protects against a deletion, a bad write or a fire. If Unraid is the answer, the failure path worth reading before it happens is Unraid disk disabled, and the parity calculator will model usable capacity for a given drive mix.

FAQ

is freenas still supported?

No. FreeNAS was folded into TrueNAS in 2020, when TrueNAS 12.0 CORE became its upgrade path, and CORE itself is no longer under active development; its last release was 13.3-U1.2 in April 2025. New installs should use TrueNAS Community Edition, the Debian-based line formerly called SCALE, currently at 25.10.7.

is truenas free?

Yes. TrueNAS Community Edition is free and open source with community support; the paid product is TrueNAS Enterprise, typically sold as turnkey appliances. That makes the software cost gap with Unraid $49 to $249, the price of a Starter, Unleashed or Lifetime licence when checked in October 2026.

does synology still require synology drives?

Not for hard drives on current models. DSM 7.3, released 8 October 2025, lets 2025 DiskStation Plus, Value and J Series units install and create storage pools on third-party drives. M.2 storage pools and cache still need listed drives, and DSM 7.4’s deduplication and compression for hard-drive volumes requires Synology hard drives.

how much ram does truenas need compared to unraid?

TrueNAS asks for at least 8 GB for basic use with up to eight drives, more with apps and VMs. Unraid sets no pool-size rule, calls 1 GB per TB a myth in its ZFS documentation and caps the ZFS cache near one eighth of RAM. Its VM guide sets 8 GB as the minimum for virtual machines.