It means the firmware has been tweaked to better behave in a NAS (usually RAID) environment. Mostly this means it won’t make heroic attempts to recover a bad sector like a normal desktop drive, instead it will let the RAID controller rebuild it from parity.
This is helpful because desktop drives in RAID arrays that go into heroic recovery mode will often seem to disappear for tens of seconds, which will cause the RAID controller to freak out and mark the whole drive dead unnecessarily.
A couple of other things are usually common among “NAS” HDDs…
As mentioned (props to @jandrese on that call), changes in firmware to ensure faster operation with a RAID controller, and fewer issues with sector mapping going berserk in trying to ensure that everything is perfect.
Either a better tolerance for vibration, or vibration reduction since a NAS or server will have multiple drives, and you don’t want interference between them. Especially true once you pass about three or four drives together.
Heat and power. Since a regular PC can often be left to idle only to be called upon for instantaneous recall, the drives have specific tuning for idling. And they get a chance to shut down fairly often-ish. Servers and NAS or SAN units typically require more uptime, and hence 24/7 performance demands while still commanding reasonable performance and power consumption.
Sometimes, but not always, a better measure of reliability. These, in particular, sit closer than most to being enterprise grade. All drives will fail, and you just hope that yours isn’t on the short end of the average spectrum (MBTF = Mean Time Between Failure), but if you buy well, you can rest more easily.
As to whether or not all of this matters really depends on your application, and there is no universal solution; unless you have infinite money, and can just scale everything on an enterprise level. But for most of us that isn’t an option. So for some folks, regular desktop drives may be fine. Some may want lower power/heat in a server. For me, as I said earlier, these have proven the best compromise on all fronts - Performance, power, heat, price, reliability.
As to brand and history, I’m not a fanboy of any particular brand of physical disk drive, owning a Seagate hybrid (in my work laptop), a Samsung Spinpoint (PS4 upgrade), and both a WD Black and Green in one of my PCs (Probably won’t buy Green again - Too slow, unreliable, and not a particularly efficient drive, when compared to NAS drives, IMHO). However, even with the Hitachi fans mourning WD’s purchase of them a few years back, these have still had a solid track record. These will, for the foreseeable future, be in my desktop builds. But probably new ones… Any model with as good a record would get my attention too.
