How long do NAS drives last?
What annualized failure rate (AFR) really means, how long NAS hard drives typically last, and how to plan for failures.
Most NAS drives run for years, not months. But a hard drive doesn't come with an expiry date - it comes with a failure rate. Plan around the rate and a dead drive becomes a routine swap instead of a bad weekend.
AFR: the only number worth trusting
Annualized failure rate is the share of a given model that dies in a year. 1% AFR means roughly 1 drive in 100 fails per year. Skip the manufacturer's MTBF figure - a "2.5 million hour" rating doesn't mean the drive lasts 285 years, it's a modelled number, not a measured one. AFR comes from real fleets running at scale. We pull it from Backblaze Drive Stats onto every drive page and into the reliability rankings, where the 2025 fleet-wide average lands around 1.4%.
How to read a model's AFR:
- Under 1% is excellent. Most 16-22TB Seagate Exos and WD Ultrastar drives sit here, around 0.5-0.7%.
- 1-2% is normal. Don't lose sleep over it.
- Over 2% earns a closer watch - and a redundancy plan that can absorb the failure without drama.
The bathtub curve
Drives fail on a predictable schedule. There's a cluster of early deaths (manufacturing duds, usually the first few weeks), then a long flat stretch where almost nothing happens, then a slowly rising tail as mechanical wear sets in past the four or five year mark. So burn a new drive in before you trust real data to it, and watch SMART closely on anything past its fourth birthday.
Plan for failure
You can't predict a single drive, so build the system so one death doesn't matter:
- Redundancy. RAID so one (or two) drives can drop with no data loss. See RAID and how many drives you need.
- Monitoring. Turn on SMART alerts and scheduled scrubs, then actually act on the warnings instead of clicking past them.
- Backups. RAID is not a backup. Keep three copies, on two kinds of media, with one off-site.
Does "NAS-rated" actually last longer?
In a NAS, yes. NAS and enterprise drives carry higher workload ratings (180-550TB/year, versus roughly 55TB for a desktop drive), 3-5 year warranties, and firmware built for 24/7 vibration-heavy bays. Where Backblaze has data on a model, rank by AFR. Where it doesn't - which covers most consumer NAS drives - lean on the workload rating and the warranty length instead.