Best 4-Bay NAS in 2026: Home and Small Business Buyer’s Guide
A 4-bay NAS sits in a sweet spot that two-bay devices simply cannot reach. With four drive bays you unlock RAID 5 and RAID 6 protection, giving you a genuine safety net without sacrificing most of your raw capacity to redundancy. Whether you are building a centralised media library for the household, setting up shared storage for a small team, or running a home lab that demands reliability, a 4-bay unit gives you the headroom to grow without paying enterprise prices.
This guide covers the best 4-bay NAS devices available in the UK in 2026, explains the RAID options you gain over a 2-bay device, walks through realistic capacity planning, and tells you honestly when it might be worth stepping up to five or six bays instead.
Who Should Buy a 4-Bay NAS?
Not everyone needs four bays. A 2-bay device handles light use cases perfectly well — a single user backing up a laptop, a small Plex library with a handful of films, or basic file sharing in a one-person household. The step up to four bays makes sense when your needs grow into one or more of the following categories.
- Families with large media libraries. 4K video files consume 50–100 GB each. A family accumulating holidays, home videos, and a Plex library in the double-digit terabytes will quickly fill two drives and have nothing left for backups. Four bays let you run RAID 5 across large drives and still have meaningful usable capacity.
- Small businesses storing shared files. A team of five to fifteen people sharing documents, design assets, or database backups needs protection against drive failure without constant IT intervention. RAID 5 on a 4-bay device means one drive can fail and the data survives, giving you time to replace the drive and rebuild.
- Home lab users and power users. Running virtual machines, Docker containers, surveillance cameras, or multiple services simultaneously puts pressure on both storage and CPU. A 4-bay device with a capable processor, expandable RAM, and PCIe expansion options keeps pace with these workloads in ways that entry-level 2-bay hardware cannot.
- Anyone who has outgrown 2-bay. If you are already mirroring two drives in RAID 1 and finding yourself rationing space, four bays let you double your raw capacity, switch to a more space-efficient RAID level, and add drives as your needs expand.
Why Upgrade from 2-Bay to 4-Bay?
The most practical reason is RAID 5. With only two drives you are limited to RAID 1 (mirroring), which uses exactly half your raw capacity for redundancy — two 8 TB drives give you 8 TB usable. RAID 5 across four drives uses just one drive’s worth of space for parity, so four 8 TB drives give you approximately 24 TB usable. That is three times the usable storage from twice the number of drives.
Beyond RAID efficiency, four bays give you room to grow incrementally. You might start with two or three populated bays and add drives later as your budget allows. With a 2-bay device you are already at capacity the moment you install both drives.
Many 4-bay devices also bring better hardware than their 2-bay siblings — faster CPUs for transcoding, more RAM slots, M.2 SSD cache ports, 2.5GbE networking, and PCIe expansion slots. The jump to four bays is often also a jump in performance class, not just storage capacity.
Our Top Picks for 2026
Best Overall: Synology DS423+
The Synology DS423+ remains the most well-rounded 4-bay NAS for home and prosumer use. It runs on an Intel Celeron J4125 quad-core processor with dedicated hardware transcoding support, meaning Plex and Synology’s own Video Station can serve 4K streams without melting the CPU. It ships with 2 GB of DDR4 RAM but accepts up to 6 GB, and there are two M.2 2280 NVMe slots on the underside for SSD caching — a feature that meaningfully accelerates random I/O on large mechanical drive arrays.
Synology’s DSM operating system is the reason many buyers choose Synology over rivals. It is polished, regularly updated, and backed by a rich ecosystem of first-party apps covering backups, cloud sync, surveillance, virtual machines, and more. The DS423+ also inherits Synology’s excellent support infrastructure and a predictable compatibility list for drives and memory.
- CPU: Intel Celeron J4125 (4-core, 2.0 GHz)
- RAM: 2 GB DDR4 (expandable to 6 GB)
- Network: 2x 1GbE
- M.2 slots: 2x NVMe (cache only)
- PCIe expansion: No
- Approximate UK price: £450–£490 (unit only)
If you want a device that just works, stays secure, and will be supported for years, the DS423+ is the default recommendation for households and small creative teams.
Best for Business: Synology DS923+
Where the DS423+ is tuned for home users, the Synology DS923+ is built for small business environments that need more compute, expandability, and networking headroom. It uses an AMD Ryzen R1600 dual-core processor — faster per-core than the J4125 for database and virtualisation workloads — and ships with 4 GB of ECC RAM, expandable to 32 GB. ECC memory detects and corrects single-bit memory errors, which matters when the NAS is serving an active business rather than an occasional media stream.
The DS923+ includes a PCIe Gen 3 x2 slot, which Synology sells an E10G22-T1-Mini 10GbE card for. For businesses where multiple users transfer large files simultaneously, 10GbE eliminates the bottleneck that 1GbE creates. It also supports Synology’s DX517 expansion unit, letting you add up to five more drives without replacing the enclosure.
- CPU: AMD Ryzen R1600 (2-core, 2.6 GHz base)
- RAM: 4 GB DDR4 ECC (expandable to 32 GB)
- Network: 2x 1GbE + PCIe slot for 10GbE upgrade
- M.2 slots: 2x NVMe (cache only)
- PCIe expansion: Yes (Gen 3 x2)
- Approximate UK price: £560–£610 (unit only)
Best for Power Users: QNAP TS-464
QNAP’s TS-464 is the choice for home lab enthusiasts and power users who want flexibility rather than a curated ecosystem. It runs an Intel Celeron N5095 quad-core processor at up to 2.9 GHz, ships with 8 GB of DDR4 RAM (expandable to 16 GB), and includes two M.2 2280 slots that can be used either for SSD caching or as storage volumes — not just cache, unlike Synology’s approach. Native 2.5GbE on both network ports means you get better-than-gigabit speeds out of the box without buying an expansion card.
The headline feature for power users is the PCIe Gen 3 x2 slot, which opens the door to 10GbE cards, additional M.2 adapters, or USB 3.2 expansion. QNAP’s QTS operating system is more complex than DSM but considerably more configurable, and the company supports running containers, virtual machines, and Linux stations directly on the hardware. If you want a device that behaves more like a general-purpose server, the TS-464 fits the brief.
- CPU: Intel Celeron N5095 (4-core, up to 2.9 GHz)
- RAM: 8 GB DDR4 (expandable to 16 GB)
- Network: 2x 2.5GbE
- M.2 slots: 2x NVMe (cache or storage)
- PCIe expansion: Yes (Gen 3 x2)
- Approximate UK price: £490–£540 (unit only)
Best Value: QNAP TS-453E
The QNAP TS-453E delivers strong everyday performance at a noticeably lower price than the TS-464 while retaining the 2.5GbE ports and generous 8 GB RAM. The processor is an Intel Celeron J6412 quad-core, which is capable enough for media streaming, file sharing, and lightweight container workloads. Unlike the TS-464, there is no PCIe slot and no M.2 cache support, so this is a device focused on straightforward storage rather than expandability.
For families or small teams whose requirements are stable — share files, run Plex, keep backups — the TS-453E covers the bases without charging for PCIe headroom they will never use. The 2.5GbE ports are a genuine upgrade over 1GbE competitors at a similar price point.
- CPU: Intel Celeron J6412 (4-core, 2.0 GHz base)
- RAM: 8 GB DDR4 (expandable to 16 GB)
- Network: 2x 2.5GbE
- M.2 slots: None
- PCIe expansion: No
- Approximate UK price: £380–£420 (unit only)
Budget Pick: TerraMaster F4-423
TerraMaster occupies the price-conscious end of the market, and the F4-423 is their strongest 4-bay offering. It uses an Intel N95 quad-core processor (a more modern architecture than the Celeron J series), ships with 4 GB of DDR4 RAM expandable to 32 GB, and includes 2.5GbE networking plus two M.2 NVMe cache slots. On paper the specifications are genuinely competitive with devices costing significantly more.
The trade-off is software maturity. TerraMaster’s TOS (TerraMaster Operating System) has improved substantially in recent years but still trails DSM and QTS in polish, third-party app support, and community resources. Drive compatibility is also a narrower list. For a budget-conscious buyer willing to do a little more research and troubleshooting, the F4-423 represents excellent hardware value. For anyone who wants everything to work out of the box, the extra spend on a Synology or QNAP is worth it.
- CPU: Intel N95 (4-core, up to 3.4 GHz)
- RAM: 4 GB DDR4 (expandable to 32 GB)
- Network: 2x 2.5GbE
- M.2 slots: 2x NVMe (cache)
- PCIe expansion: No
- Approximate UK price: £300–£350 (unit only)
4-Bay NAS Comparison Table
| Model | CPU | RAM (stock / max) | Network | PCIe slot | M.2 slots | Approx. UK price |
|---|---|---|---|---|---|---|
| Synology DS423+ | Intel Celeron J4125 | 2 GB / 6 GB | 2x 1GbE | No | 2x NVMe | £450–£490 |
| Synology DS923+ | AMD Ryzen R1600 | 4 GB ECC / 32 GB | 2x 1GbE + PCIe 10GbE | Yes (Gen 3 x2) | 2x NVMe | £560–£610 |
| QNAP TS-464 | Intel Celeron N5095 | 8 GB / 16 GB | 2x 2.5GbE | Yes (Gen 3 x2) | 2x NVMe | £490–£540 |
| QNAP TS-453E | Intel Celeron J6412 | 8 GB / 16 GB | 2x 2.5GbE | No | None | £380–£420 |
| TerraMaster F4-423 | Intel N95 | 4 GB / 32 GB | 2x 2.5GbE | No | 2x NVMe | £300–£350 |
Prices are approximate retail figures as of early 2026 and will vary by retailer. Amazon UK, Scan, and Ebuyer are the main UK stockists for all models above.
RAID Options for a 4-Bay NAS
With four drives you have meaningful choices about how to protect your data. Here is a plain-English explanation of the main options.
RAID 5 — The Most Popular Choice
RAID 5 stripes data and parity across all four drives. If any single drive fails, the parity information on the remaining drives allows the array to reconstruct the lost data when you replace the failed drive. With four drives you lose the equivalent of one drive’s capacity to parity, so four 8 TB drives give you roughly 24 TB of usable storage.
RAID 5 is the go-to choice for home and small business use because it strikes the best balance between capacity efficiency, performance, and fault tolerance. The main risk is a second drive failure during a rebuild — modern large drives take many hours to rebuild, and if a second drive fails in that window, you lose everything. For this reason, always keep a spare drive on the shelf.
RAID 6 — Extra Protection at a Capacity Cost
RAID 6 uses two sets of parity instead of one, meaning two simultaneous drive failures can be survived. The cost is two drives’ worth of capacity devoted to parity, so four 8 TB drives give you 16 TB usable — the same as RAID 1 mirroring on two drives, but with four drives.
RAID 6 is worth considering if you are using high-capacity drives (16 TB and above, where rebuild times are very long), if the data is genuinely business-critical, or if the NAS is in a location where a second drive failure during rebuilding feels like a realistic risk. For most home users, RAID 5 with a spare drive on hand is sufficient.
RAID 10 — Speed and Redundancy, Lower Capacity
RAID 10 (also called RAID 1+0) mirrors pairs of drives and then stripes across those mirrors. With four drives you get two mirrored pairs, giving 50% usable capacity — four 8 TB drives yield 16 TB. In return you get excellent read and write performance and the ability to survive one failure in each mirror pair simultaneously.
RAID 10 is most useful when performance is the priority over capacity — for example, a database server or a NAS serving many concurrent users with mixed read/write workloads. For straightforward file storage and media streaming, RAID 5 is the better trade-off.
JBOD and SHR (Synology Hybrid RAID)
Synology devices also support SHR (Synology Hybrid RAID), which automatically manages RAID levels and allows mixing drives of different sizes more efficiently than standard RAID 5. If you are adding drives incrementally or mixing old and new drives, SHR is worth understanding before you format your array. QNAP has a similar feature in QTS. Both allow you to expand storage volume by adding larger drives one at a time.
Capacity Planning: How Much Usable Storage Do You Actually Get?
The table below shows approximate usable storage for a 4-drive RAID 5 array at common drive sizes. These figures assume all four bays are populated with identical drives.
| Drive size (each) | Raw total | RAID 5 usable (~) | RAID 6 usable (~) | RAID 10 usable (~) |
|---|---|---|---|---|
| 4 TB | 16 TB | 12 TB | 8 TB | 8 TB |
| 8 TB | 32 TB | 24 TB | 16 TB | 16 TB |
| 12 TB | 48 TB | 36 TB | 24 TB | 24 TB |
| 16 TB | 64 TB | 48 TB | 32 TB | 32 TB |
| 20 TB | 80 TB | 60 TB | 40 TB | 40 TB |
A practical starting point for most households is 4x 8 TB drives in RAID 5, giving approximately 24 TB usable at a total drive cost of roughly £300–£400 using Seagate IronWolf or WD Red Plus drives. That is enough for a very large Plex library, years of photos and videos, and still have room for backups and other files.
If you are buying for a business, factor in annual data growth. A team generating 1–2 TB of new data per year on 4x 8 TB RAID 5 (24 TB usable) has a comfortable runway of ten or more years — though in practice you will likely want to migrate to newer, larger drives well before that point.
When to Consider a 5-Bay or 6-Bay Instead
A 4-bay NAS is the right tool for most home and small business buyers in 2026, but there are specific situations where stepping up to five or six bays is worth the additional cost.
- You need RAID 6 without sacrificing capacity. On a 4-bay device, RAID 6 wastes half your drives on parity. On a 6-bay device, RAID 6 uses only two of six drives for parity, leaving four drives for data — 67% efficiency rather than 50%. If you want double-parity protection and good capacity efficiency, six bays is the minimum sensible configuration.
- You have an existing drive collection. If you already own five or six drives from a previous system, a matching enclosure avoids drives sitting idle.
- You are running a small business with rapidly growing data. A 6-bay device future-proofs your storage without requiring a new enclosure purchase in 18 months. The incremental price difference between a 4-bay and 6-bay enclosure is often smaller than the disruption of migrating to new hardware mid-growth.
- You are running a dedicated surveillance system. IP cameras generate continuous write workloads that benefit from spreading the load across more drives. A 6-bay or 8-bay device with surveillance-grade drives is a more appropriate starting point for six or more cameras recording continuously.
The Synology DS1522+ (5-bay) and DS1621+ (6-bay) are the natural step-ups from the DS923+ for Synology users. QNAP offers the TS-664 and TS-873A for equivalent QNAP-ecosystem expansion. Both families use the same hard drives and largely the same management interfaces, so upgrading within a manufacturer’s ecosystem is relatively straightforward.
Final Recommendations
For most readers, the decision comes down to ecosystem preference and budget rather than raw specifications. Synology’s DS423+ remains the safest all-round recommendation — excellent software, reliable hardware, and strong long-term support. If you need business-grade ECC memory and future 10GbE connectivity, the DS923+ is the upgrade path within that ecosystem.
QNAP’s TS-464 is the better choice for technical users who want maximum hardware flexibility and are comfortable managing a more complex operating system. The TS-453E hits an attractive price point if PCIe expansion is not needed. And if budget is genuinely tight, the TerraMaster F4-423 delivers competitive specifications — just go in with eyes open about the software maturity gap.
Whichever device you choose, populate it with NAS-rated drives — Seagate IronWolf, WD Red Plus, or Toshiba N300 are the standard recommendations in the UK — and set up RAID 5 as your foundation. A 4-bay NAS with the right drives and a sensible RAID configuration will serve a home or small business reliably for many years.
