What do you have to look at when choosing a hard drive for a NAS? First and foremost that it is quiet and economic when it comes to power usage. It is useful if a device that will be on for 24 hours a day is not very noisy. The power usage should speak for itself: you want to pay as little as possible, but more important is that the drives will also run less hot: the power consumption determines how much excess heat is generated. Lastly the durability is very important as well, although this is unfortunately not easy to test.
Manufacturers make it slightly easier by developing drives specifically meant for use in NAS-devices. These differ in some ways compared to ‘regular’ drives. First of all they have a feature that is mostly known under the term that Western Digital uses, time-limited error recovery (TLER). With TLER the drive will not try as long to read a bad sector, because the RAID-controller will conclude that the drive is broken if it does not receive an answer from the drive. This means that it is thrown out of the RAID-array. Although, in theory. Most modern NAS-devices do not suffer from this. Without NAS or raid you want the drive to try its best in order to correct faults, meaning you will not want TLER.
Aside from that, manufacturers also claim that their NAS-drives have all sorts of special features- for example that they vibrate less and even that every drive has a slightly different rotation speed in order to prevent resonance with other drives. Unfortunately this is not testable, so we cannot say for certain if it is true or not. However, there is a longer warranty: NAS-drives have at least three years of factory warranty, while with regular drives this is mostly two and sometimes even one year (the legal obligation to have at least two years of warranty is for shops and not manufacturers).
Another important aspect is the rotation speed. The products in this test come in three different flavors: 5400, 5900 and 7200 rpm. A higher rpm normally means a faster drive, but the downside to this is that they produce more heat and noise. This is something you do not want with a NAS-drive; therefore these usually have a relatively low rotation speed.
Because of these features you also pay slightly more for the special NAS-drives. For example: if we compare the price of the cheapest 3 TB NAS drive (HGST Deskstar NAS 3 TB) with that of a regular hard drive (Toshiba DT01ACA300 3TB), we see that the NAS-drive costs about 35 pounds / 40 euros more. This might not seem that much, but based on the price of the Toshiba this is about 40%.