Unraid Hardware Guide: What to Buy for a First Build

Most first Unraid builds do not fail on performance. They fail on three decisions that are cheap to get right up front and expensive to undo later: a licence tier that runs out of device slots, a parity disk too small to grow into, and solid-state drives put in the wrong place. This guide works through the buying decisions in the order the licence and the storage model actually constrain them.

Start with the licence, not the case

Unraid is paid software with a perpetual licence, and the tier you buy caps how many storage devices the server may have attached. That cap, not the number of drive bays in the chassis, is the real ceiling on a build.

Tier	Price	Storage devices	Updates included
Starter	$49 one-time	6 devices	1 year
Unleashed	$109 one-time	Unlimited	1 year
Lifetime	$249 one-time	Unlimited	Lifetime

Starter and Unleashed keep working indefinitely after the first year; the $36 annual extension fee only buys continued access to future updates. The licence itself does not expire even if you never pay it.

The detail that trips people up is what counts as a device. Unraid’s licensing FAQ defines attached storage devices as every device present before the array starts, excluding one eMMC device and one USB device. Parity disks count. Cache pool SSDs count. An unassigned drive sitting in a bay counts. A Starter licence with six slots therefore looks like this in practice:

• 1 parity disk
• 3 data disks
• 2 cache pool SSDs

That is a complete, sensible server and it is already full. Add a second parity disk or a scratch drive for downloads and you are over the limit, and the setup documentation is explicit about the consequence: the array will not start if you exceed the number of storage devices your licence key permits. Unraid offers a free 30-day trial with no device limit, extendable twice by 15 days for a 60-day maximum, and all sales are final, so the trial is the place to confirm the device count you actually need before paying.

If the chassis has more than six bays, buy Unleashed outright. Starting on Starter and upgrading later costs $49 plus a $69 upgrade fee, which is $118 against $109 for buying Unleashed in the first place.

The boot device is part of the licence

Unraid boots from a USB flash drive, and the licence is bound to that drive’s GUID. Two consequences follow. First, the flash drive must report a genuine unique GUID; many cheap and counterfeit drives do not, and Unraid’s own setup documentation warns about this. Second, the boot drive is a single point of failure that is trivial to back up and easy to forget, so take a backup of it during setup rather than after the first problem.

Unraid 7.3 and later can also move the operating system to a supported internal boot device, either one device or two mirrored devices, chosen during the onboarding wizard. A USB drive is still needed to start a new server for the first time even if internal boot is the goal.

Capacity is irrelevant here; any size works, and speed is irrelevant too. Brand is the part that is counter-intuitive. The documentation steers away from the most recognisable names precisely because they are the most recognisable: SanDisk, Kingston and Samsung are the brands most often counterfeited, and counterfeit drives frequently have no unique GUID. Less-copied brands such as TeamGroup, Transcend and PNY are the ones it suggests, bought from a reputable retailer rather than an auction site, an unknown seller, or the second-hand market.

Buy the parity disk first

Unraid’s array does not stripe data. Each data disk holds an independent filesystem and each file lands whole on one disk, which is why the array tolerates mixed drive sizes that a RAID set would reject. The full mechanism is covered in how Unraid storage works.

The sizing rule that matters at purchase time is short: no data disk can be larger than the smallest parity disk. Unraid’s manual states it as a driving principle, use your largest drives for parity, and the reason is expansion. A 12 TB parity disk permanently caps every future data disk at 12 TB until parity is replaced first, which means an extra rebuild cycle and an extra drive purchase.

With dual parity, both parity disks must be at least as large as the largest data disk, but they do not have to match each other.

Practical version of the rule:

• Buy the biggest drive in the build as parity, even if the data disks are second-hand or smaller.
• If the plan is to grow into 20 TB drives eventually, buy 20 TB parity now.
• Second parity is worth adding once the array holds enough disks that a second failure during a multi-day rebuild is a realistic risk.

To see how a specific drive mix works out in usable capacity and rebuild time, the parity calculator on this site models mixed-size arrays with single and dual parity.

SSDs belong in pools, never in the array

Unraid does not support TRIM or Discard for SSDs assigned to the main array, which degrades their performance over time. The manual is explicit about this: put SSDs in cache pools or leave them as unassigned devices, where those features work properly.

A cache pool is one or more devices outside the parity-protected array. Writes land there at full device speed and the mover migrates them to the array on a schedule, typically overnight. Pools default to BTRFS, which is deliberate: a single-device pool formatted BTRFS or ZFS can have a second device added later to become a mirror, whereas an XFS single-device pool has to be reformatted first.

The important safety point is that a single-device pool has no redundancy. Anything on it that has not yet moved to the array is lost if it dies, and application data for Docker containers and virtual machines is normally configured to stay on the pool permanently rather than move. Two SSDs in a mirrored pool is the right default for anything running containers.

Write speed is a configuration choice, not a hardware one

Unraid’s manual publishes typical throughput per write mode, which is worth reading before spending money on drives:

Write mode	Typical speed	Drives spun up	Protected
Read/Modify/Write (default)	20 to 40 MB/s	Parity and target disk only	Yes
Turbo write (reconstruct)	40 to 120 MB/s	All drives	Yes
Cache write, SATA SSD	50 to 110 MB/s	Cache only	No, until moved
Cache write, NVMe	250 to 900 MB/s	Cache only	No, until moved

The default mode is slow because every write reads the old data and the old parity before writing both back. Faster disks barely move that number. A cache pool does, which is another argument for spending the storage budget on a decent NVMe pool rather than on faster array disks.

CPU, RAM and the controller

The array itself is undemanding. Parity is a cheap calculation and the workload that actually sizes the CPU is whatever runs on top: containers, virtual machines and any media transcoding.

Memory follows the same logic. If the build uses ZFS pools, ignore the old “1 GB of RAM per TB of storage” advice, which Unraid’s own ZFS documentation calls a myth; Unraid caps the ZFS adaptive replacement cache at roughly one eighth of system RAM so it cannot starve containers and virtual machines. Buy RAM for the virtual machines, not for the pool.

For the disk controller, the important behaviour is that Unraid identifies disks by serial number and size rather than by SATA port, so drives can be moved between ports freely when chasing a bad cable. Prefer a proper SAS host bus adapter in IT mode over port multipliers, and avoid daisy-chained SATA power splitters: unstable power delivery through splitters is one of the documented causes of the CRC errors that eventually get a disk marked as failed. That failure path is covered in Unraid disk disabled.

Networking and power

Single-file reads from the array come off one disk, so a 10 gigabit network card does not make array reads faster. What it does do is let a fast cache pool saturate the link during large transfers, which is the only case where the upgrade is clearly worth it. Where a build justifies it, the Intel X550-T2 is a genuine Intel dual-port 10GBASE-T card rather than one of the many third-party clones built on the same controller.

The other number worth knowing before committing to a design is idle power draw, because this machine runs continuously. A plug-in meter such as the Kill A Watt P3 P4400 settles arguments about spin-down policy and drive count faster than any spreadsheet.

Finally, buy an uninterruptible power supply. Unraid automatically starts a parity check after an unsafe shutdown, and unexpected power loss is the most common cause of one.

What not to buy

• SSDs intended for the parity-protected array. No TRIM, no benefit.
• A parity disk sized for today’s data disks rather than the ones you will buy next.
• A USB flash drive from an auction site or an unknown seller, whatever the brand on it says. A counterfeit has no unique GUID and cannot be licensed.
• More drives than the licence tier allows. The array will not start.
• A single cache SSD if containers or virtual machines will live on it.

If you are still deciding between Unraid and the alternatives before spending anything, Unraid vs TrueNAS vs Synology compares the three storage models on expansion, redundancy and failure behaviour.