Best 4-Bay NAS 2026 — Live Prices & Picks

Why 4 bays

Four bays is the size the NAS market is actually fought over, and it shows in the table below: every brand we track fields a 4-bay, from TerraMaster's budget x86 boxes through UGREEN's 10GbE value plays to Synology's software flagships and Asustor's M.2-stacked Lockerstor. The reason is arithmetic. RAID 5 across four drives yields three drives of usable capacity with one-drive fault tolerance — the first configuration where redundancy stops costing you half your disks, and the last size that still fits under a desk unnoticed.

The buying decision at four bays is therefore rarely about bays at all — it is the brand trade-off in miniature. The same money buys polish (Synology), expansion (QNAP), raw specs (UGREEN), or maximum drives-per-dollar (TerraMaster), and the live prices below quantify each premium in real time. Whichever direction you lean, four bays is the configuration our hub's worked example prices, the size our NAS Builder defaults to, and the safest recommendation for a first serious NAS.

Four bays is also where the second-hand question first gets interesting: the used market prices retired 4-bay enclosures aggressively, but in the current climate we recommend against used enclosures while recommending recertified drives — the enclosure carries the failure modes you cannot inspect (backplane, PSU, fans) at a discount too small to compensate, while recertified drives arrive tested, warrantied and cheaper per terabyte. Buy the enclosure new from the live table; save on the drives instead.

Storage math at 4 bays

Run RAID 5 as the default: with four 20TB drives that is 60TB usable and any single drive can fail. The caveat that matters in 2026 is rebuild exposure — replacing a failed 20TB drive means a rebuild window measured in a day or more, during which a second failure is fatal. That risk is manageable at four bays with a verified backup and prompt drive replacement, but it is why RAID 6 (two-drive tolerance, two drives of usable space lost) is worth considering once your drives are large and your tolerance for re-ripping a library is low.

SHR on Synology and mixed-size support on UnRAID-style setups add flexibility four bays exploit well: you can start with two drives and add two more later, or mix sizes during an upgrade cycle. Model your exact configuration in the RAID planner, and if you are filling the bays over time rather than at once, buy the largest drives you can afford first — the small ones you buy today become the array's ceiling tomorrow.

One scheduling habit completes the four-bay setup: a monthly data scrub. Parity RAID only detects latent sector errors when it reads them, and a scrub reads everything — finding the quiet failures while the array is healthy instead of during a rebuild, which is the worst possible moment for surprises. Every OS in the table above can schedule scrubs; enabling it is ten seconds of configuration that materially changes RAID 5's real-world safety at this drive size.

Model any drive count and RAID level in the RAID planner, and compare drive prices per terabyte on the NAS drive tracker. Upgrading an existing array instead? The upgrade planner nets out the resale value of the drives you retire.

What to look for in a 4-bay

Differentiators worth paying for at this size, in order: an Intel CPU with Quick Sync if any media serving is on the menu (UGREEN's lineup and QNAP's TS-464 own this), 10GbE if you move large files routinely (UGREEN DXP4800 Plus ships it standard; QNAP adds it later via PCIe), ECC memory if the box carries business data (Synology DS925+, Asustor Gen3), and NVMe slots for caching only once you know your workload actually benefits. Skip paying for: RAM beyond 8GB on a pure file server, and any bundle that includes drives — our live drive trackers will beat bundle pricing.

A practical selection sequence that avoids analysis paralysis: eliminate models that fail your hard requirements (transcoding, 10GbE, ECC), then among survivors take the cheapest live price unless a specific software need argues otherwise. The table re-sorts itself every two hours, and the honest truth about the current 4-bay market is that every surviving model in it is good — the era of bad mainstream NAS hardware is over, which moves the entire decision to price and OS fit.

Drives for a 4-bay

Four bays reward disciplined drive buying. Purchase all four together from one order — matched capacity, CMR recording, ideally NAS- or enterprise-class — and record each serial's SMART baseline on arrival. The per-terabyte sweet spot moves weekly in this market; our live trackers currently make the case for either new NAS drives in the mid-capacities or recertified enterprise pulls above them, and the right answer is whichever is cheaper per terabyte on the day you order, not a brand loyalty.

One sizing insight specific to RAID 5: capacity upgrades later require replacing all four drives before any new space appears, so the drives you buy today set the array's economics for years. That is the argument for stretching to the next capacity tier now if the per-terabyte price is close — and it is exactly the calculation the upgrade planner runs in reverse when the time comes, crediting the resale value of the four drives you retire.

Mistakes to avoid at 4 bays

The most expensive 4-bay mistake is buying it for RAID 5 and configuring RAID 0 or JBOD 'temporarily' to get all the space — temporary becomes permanent, and a single drive failure then takes everything. Configure the parity array on day one, before data arrives, because converting later usually means a full wipe and restore.

Second: skipping the backup because RAID feels safe. One drive of parity protects availability, not history — deletion, ransomware and the enclosure itself failing are all outside its coverage. Third: buying an ARM or bottom-tier Celeron 4-bay for a Plex household. Transcoding needs land on the CPU list above everything else at this size, and the Intel iGPU models carry a modest premium in the live table for a capability you cannot add later. Fourth, and most 2026-specific: ignoring the drive bill until checkout — at today's prices four drives routinely cost two to three times the enclosure, which is why the builder tool prices the whole build, not the box.

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