The best NAS hard drive is the one built for always-on use, with the right recording type and a size that fits your plan. Drives are the part of a NAS you will spend the most on and rely on the most, and a few specifications explain most of the difference between a good choice and a painful one.
Buy drives made for NAS use
NAS-rated drives are designed to run around the clock, tolerate the vibration of neighbouring drives and report errors in a way RAID controllers handle gracefully. Desktop drives are built for fewer power-on hours.
CMR vs SMR
CMR (conventional) drives write data in a straightforward way and handle sustained writes and array rebuilds well. SMR (shingled) drives pack tracks more tightly, which can make long writes and rebuilds very slow. For RAID arrays, CMR is the safer default, so check the specification sheet before you buy.
Capacity and speed
Larger drives lower your cost per terabyte and use fewer bays, but they take longer to rebuild. 5,400 RPM class drives run cooler and quieter, while 7,200 RPM drives can be faster for heavy workloads.
Which size: 4TB or 8TB?
Size decides how many bays you need and how long rebuilds take. Our comparison of a 4TB vs 8TB NAS hard drive walks through the trade-offs, and the RAID calculator shows the usable space.
Reduce correlated failures
If possible, mix purchase dates or batches rather than buying every drive from the same box, and replace drives promptly at the first warnings.
