Your NAS is only as good as the drives inside it. We break down why CMR is mandatory and which 20TB+ monsters are worth the money.
By The Server Team
EasyDriveCompare.com
If you take one thing away from this guide, let it be this: Never put an SMR (Shingled Magnetic Recording) drive in a RAID array.
Why? SMR drives overlap data tracks to save space. When you try to overwrite data (like during a RAID rebuild), the drive has to rewrite adjacent tracks too. This causes massive slowdowns. Your NAS will think the drive has failed, kick it out of the array, and potentially crash your storage pool.
Always buy CMR (Conventional Magnetic Recording) drives. For a broader look at all storage types — SSDs, HDDs, and NAS — see our full storage guide.
| Drive Series | Best For | Workload/yr | Warranty | RPM |
|---|---|---|---|---|
| WD Red Pro | Medium/Large Business (24/7) | 300TB | 5 Years | 7200 |
| WD Red Plus | Home / SOHO (1–8 bay) | 180TB | 3 Years | 5400 |
| Seagate IronWolf Pro | Creative Pros (High Speed) | 300TB | 5 Years | 7200 |
| Toshiba N300 | Budget Value | 180TB | 3 Years | 7200 |
Capacity is what you actually pay for, so price-per-terabyte matters more than the sticker price. These are live UK prices from our comparison data, last checked 2026-07-27.
| Drive | Capacity | Price | Price per TB |
|---|---|---|---|
| Seagate IronWolf Pro 16TB | 16TB | £560.00 | £35.00 |
| Seagate IronWolf 2TB, Enterprise Internal NAS HDD | 2TB | £130.00↓ 6% | £65.00 |
The pattern to notice: the cheapest drive per terabyte is rarely the cheapest drive. Small NAS drives carry a steep £/TB premium, which is why buying one larger drive usually beats two small ones — provided your bays and rebuild times allow it.
Once you go above 10TB or 12TB, manufacturers switch from air-filled drives to Helium-filled. If you need portable storage rather than NAS drives, see our external hard drives comparison instead.
Cooler Running: Helium creates less friction, so drives run 4-5°C cooler.
Less Power: Lower friction means less energy usage (crucial for 24/7 servers).
Quieter: No turbulence means less "whirring" noise.
For most 1–8 bay home and SOHO setups, the WD Red Plus and Seagate IronWolf are the sweet spot: both are CMR, purpose-built for 24/7 NAS use, and rated for a 180TB/year workload. Buy the largest capacity you can afford on a price-per-terabyte basis rather than several small drives, because small NAS drives carry a steep £/TB premium and every extra drive is another thing that can fail.
Use CMR. SMR (Shingled Magnetic Recording) drives overlap data tracks, so overwriting data — exactly what a RAID rebuild does — forces the drive to rewrite adjacent tracks. This can slow the drive so badly that the NAS marks it as failed and drops it from the array. Always confirm a drive is CMR before putting it in a RAID pool.
They are closely matched. WD Red Plus (5400-class) runs cooler and quieter, which suits a NAS living in a bedroom or office. Seagate IronWolf spins at 7200 RPM for slightly faster throughput but runs a little warmer and louder. Both are CMR with a 3-year warranty and a 180TB/year workload rating, so pick on price-per-terabyte and whether noise or speed matters more to you. Step up to the Pro versions (Red Pro / IronWolf Pro) for a 5-year warranty and a 300TB/year workload in busier arrays.
The workload rating is how much data the manufacturer expects you to read and write per year while keeping the warranty valid. Home NAS drives like WD Red Plus and IronWolf are rated for 180TB/year, which is plenty for backups, media and light file sharing. Busy multi-user arrays, surveillance, or constant syncing can exceed that, which is when the 300TB/year Pro drives are worth the premium.
Usually one larger drive. The cheapest drive per terabyte is rarely the cheapest drive: small NAS drives carry a steep £/TB premium, and fewer drives means lower power draw and fewer points of failure. The caveats are that you need spare bays for future expansion and redundancy, and that very large drives take longer to rebuild after a failure — so balance capacity against your bay count and RAID level.
Don't risk your data on cheap drives. Compare prices on the best CMR NAS drives and build a server that lasts.
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