A cheap 8TB drive can look like a bargain until it lands in a NAS, starts rebuilding after a disk failure, and takes far longer than expected. That is the real problem behind how to choose a NAS drive: the lowest price is not always the lowest-cost option once reliability, rebuild time, noise and usable value are factored in.
For most UK buyers, a NAS drive decision comes down to three things: what the box is for, how many bays it has, and whether the price per terabyte still makes sense after you filter out unsuitable models. A family backup NAS, a Plex library and a small business file server do not need exactly the same drive, even if they all use 3.5-inch hard disks.
How to choose a NAS drive without overpaying
Start with the job, not the brand. If your NAS is mainly for nightly backups, archived photos and occasional file access, you usually want the lowest sensible £/TB from a drive built for NAS use. If it will run all day with multiple users, constant syncing, cameras, virtual machines or media streaming, you should care more about workload rating, vibration handling and warranty.
That is where buyers often get caught out. They compare two drives with the same capacity and assume the cheaper one is better value. Sometimes it is. Sometimes it is a desktop drive, an SMR model, or simply priced low because it is less suited to RAID and sustained write workloads.
A value-first comparison should look at capacity, drive type, recording method, warranty and £/TB together. Headline price on its own is not enough.
Capacity matters more than most people expect
Capacity affects both value and rebuild risk. In many parts of the UK market, NAS hard drives hit the best £/TB somewhere in the mid-to-high capacities rather than the smallest models. A 4TB drive may look affordable, but the £/TB is often worse than 8TB, 12TB or 16TB options.
That said, the cheapest capacity band is not always the best buy for your setup. In a two-bay NAS, buying two very large drives can cost more up front than you need. If you only need 4TB of usable space today, paying extra for 24TB raw capacity is poor value even if the £/TB looks attractive.
There is also the rebuild trade-off. Larger drives usually improve £/TB, but they can take longer to rebuild after a failure. For home users this may be an acceptable trade. For a busy small office, longer rebuild windows increase risk and may justify paying more for a better-spec drive or a different RAID layout.
As a rough rule, buy enough capacity for your current data plus sensible growth for the next few years. Do not buy so little that you fill the NAS in months, but do not chase huge capacities just because they top the value table.
A quick way to size it
Estimate your real data total, add room for growth, then account for redundancy. If you need 6TB usable and plan to mirror in a two-bay NAS, you need at least 12TB raw. That usually means 2 x 6TB minimum, but in practice 2 x 8TB may offer better value and more breathing room.
CMR vs SMR is not a small detail
If you only remember one technical point from this guide, make it this one. For NAS use, CMR drives are usually the safer choice. SMR drives can be fine for light, infrequent writing, but they are less desirable in RAID and NAS workloads because write performance can drop sharply during sustained activity, rebuilds or parity operations.
That does not mean every SMR drive is unusable. It means you should not buy one by accident just because the price looks good. For a single external backup disk, SMR may be acceptable. For a multi-bay NAS expected to stay online and handle regular writes, CMR is usually worth the extra cost.
This is a classic value trap. A cheaper SMR disk can have a lower purchase price but worse practical value if it causes slow rebuilds, inconsistent performance or extra hassle later.
NAS drive, desktop drive or enterprise drive?
Most buyers should start with NAS-labelled drives from lines such as Seagate IronWolf or WD Red Plus and then compare £/TB across capacities. These are aimed at 24/7 operation, multi-bay systems and vibration-aware use cases. That makes them the default middle ground for home and small business NAS boxes.
Desktop drives can be tempting when they are much cheaper. If you are building a very low-cost home NAS for light backups and one or two users, they may work, but you are accepting more risk. They are not usually the best fit for RAID-heavy, always-on use.
Enterprise drives often offer stronger workload ratings, longer warranties and better durability on paper. The problem is price. If the £/TB premium is small, they can be worth considering for heavier workloads. If the premium is large, many home users are paying for headroom they will never use.
The right choice depends on workload. A family media and backup box usually does not need enterprise-spec disks. A small office with constant file access might.
Check the workload, bays and warranty
Manufacturers do not only segment by capacity. They also segment by workload rating, supported bay count and warranty length. Those details help explain why two 12TB NAS drives can be priced quite differently.
For a basic two-bay or four-bay home NAS, mainstream NAS drives are normally enough. If you are filling an 8-bay unit, running RAID with several users, or keeping the NAS busy day and night, drives designed for higher vibration environments are worth a look.
Warranty is one of the easiest ways to sanity-check pricing. If one drive is only slightly cheaper but comes with a shorter warranty or a weaker NAS spec, the saving may not be enough. On the other hand, if a drive with a longer warranty costs materially more per terabyte, ask whether your use case justifies it.
Noise, power and heat are practical buying factors
NAS boxes do not sit in a server room for most home buyers. They sit in a study, spare room or under the telly. That makes acoustics matter more than many comparison tables suggest.
Higher-capacity and higher-performance hard drives can be noisier. Enterprise models in particular may produce more vibration and seek noise than buyers expect. If your NAS lives in a shared space, paying slightly more for a quieter mainstream NAS drive can be the better decision.
Power and heat also affect running costs and comfort. The difference per drive may not be huge, but in a multi-bay system that runs all year, it adds up. This does not override purchase price, but it is part of real value.
SSDs in a NAS are a different value equation
Some buyers asking how to choose a NAS drive are really deciding between NAS HDDs and NAS SSDs. For most bulk storage, hard drives still win clearly on £/TB. If your goal is cheap capacity for backup, media or archives, HDDs remain the sensible buy.
SSDs make more sense when you need quiet operation, low power use, fast random access or a cache layer. They are usually poor value for large-capacity NAS storage unless your workload specifically benefits from the speed. A media archive, for example, often does not.
If you are trying to build the cheapest practical NAS, start with HDDs and only pay the SSD premium where there is a clear workload benefit.
Compare by £/TB, but filter the data first
This is where a site like TerabytePrices is most useful. Price per terabyte is the quickest way to spot market outliers, but only after you narrow the field to drives that actually suit NAS use.
First filter for NAS-capable models in the right form factor and capacity range. Then compare £/TB across those results. That stops a cheap but unsuitable desktop or surveillance drive from distorting the shortlist.
After that, check whether a higher capacity has a meaningfully better £/TB. Sometimes moving from 8TB to 12TB improves value enough to justify the extra spend. Sometimes the step up is expensive and the lower capacity is the smarter buy.
Also watch for misleading discounts. A drive marked down by 20 per cent may still have a worse £/TB than a similar model without the badge. The real question is not whether it is on offer, but whether it beats the alternatives in the same class.
The short version for most buyers
If you want the safest mainstream choice, buy a CMR NAS hard drive from a known NAS range, choose a capacity that leaves room for growth, and compare only against similar NAS models on £/TB.
If your NAS is for light home backup, value matters most and you can stay in the mainstream NAS category. If it is for heavy multi-user or always-busy work, spending more on better-rated drives may be justified. If a drive is unusually cheap, check whether it is SMR, a desktop model, or simply poor value once warranty and specs are considered.
A NAS drive is not a place to chase the absolute bottom price. It is a place to avoid false economy. Buy for the workload, compare on real cost per terabyte, and let the numbers talk louder than the discount sticker.