Home server:
- two 14 TB enterprise drives + two 6 TB Red Plus drives in my main storage pool (ZFS, mirrored)
- one 4 TB WD Red Pro, mostly just as a place to stick Steam installs when I'm not using them
- three 2 TB Red Plus, miscellaneous backup/scratch storage, mostly because I had them and they still work
I also have four 6 TB + one 2 TB drives (Red Plus) in my "secondary" rig. These are in a mergerfs+snapraid pool, whose job is to store automated backups of the server's main pool.
And then there are external drives, which I use for periodic "offline" backups. Most of the time these are disconnected. All told, I think I have 104 TB of raw HDD storage, but once you subtract parity drives and backup storage, you're looking at about a third of that in usable space.
I no longer run HDDs in my main "gaming" rig, though I'm not opposed to doing so. About a year ago I had to RMA the gaming rig's HDD. In the interim I got a bizarre urge to mod the case. Now there's nowhere to put the HDD cages.
To echo others in the thread, HDDs aren't going anywhere. They're cheap; they're reliable; they don't need to be powered on to retain data integrity, and they're plenty fast enough for the most obvious bulk-storage use cases. If we're comparing to new(ish) NVME SSDs, it's worth pointing out that cooling is easier to manage too. In my personal experience, SSDs not only fail more often; they're also prone to sudden catastrophic failure, whereas HDDs tend to give you ample warning. You can even configure SMART to run automated tests and mail you if there's a problem.
On the con side, HDDs can be noisy. During a scrub, I can hear the enterprise drives in the next room. It isn't an unpleasant sound, but it is there.
I went out of my way to mention "Red Plus" because that's WD's most affordable NAS drive that isn't SMR. Avoid vanilla Reds. I'd also avoid the likes of Seagate Barracuda or WD Green. In my 30 years of collecting HDDs, I've only ever had two outright failures, both from Seagate's notoriously tainted batch of dirt cheap Barracudas in ~2013. I also had an old Toshiba laptop HDD that started throwing errors after about ten years. It still worked, but I threw it out. The aforementioned RMA from my gaming rig was a WD Red Pro, which never threw any SMART errors, but it did start clicking about three years in. WD replaced it without complaint.
For affordable enterprise drives, there are
compelling refurbished options.
EDIT: If you do buy enterprise drives (Exos, Ultrastar), though, keep in mind that their mounting scheme might not exactly match with your case's mounting scheme (see
here and
here. Also, some of the enterprise models have
a disable feature on the 3.3v pin, which may not be compatible with all power supplies out of the box. You can fix this by covering the relevant pin with kapton tape, or you can sidestep the issue by referencing
spec sheets before buying. (These issues can also arise with consumer drives, but they're much less common, mostly relevant to people who shuck external drives.)
There's what you might call a price-reliability sweet spot. Even the most reliable HDD in the history of the planet, by itself, would offer less peace of mind than two middling drives with one set as back up. On the other hand, if you buy the cheapest crap HDDs, even having a back up or two probably won't help you sleep at night--sure, you can recover in the event of failure, but you don't want to go through that process on a regular basis.
Opinions will differ on how exactly to reach that sweet spot, but FWIW my recs are in the previous post (which the forum auto-folded into this post, lol)--Red Plus (or Pro, if you want a little extra warranty in return for a higher price), or refurbished enterprise drives, which might fail but again you're getting such an enormous discount on the storage space that they're a no brainer for redundant (parity + backup) schemes.
Avoid shingled drives (SMR) at all costs. There are references to double check whether a given model is SMR or CMR.
This one, for example.