Hard disk for Music Server

I’d go with cheap drives in a decent NAS enclosure connected via Ethernet.

That’s certainly a reasonable suggestion, Erik, **if** (IMO) it is supplemented by an additional backup on a completely separate drive or set of drives. For example, if the power supply in the NAS enclosure goes berserk it could simultaneously wipe out all of the drives that are contained. Or if the controller circuitry in the enclosure fails at some point in the future, and the same or a similar enclosure is no longer available, depending on what RAID mode is being used the data may be unrecoverable.  Or if there is a latent bug in the controller firmware, that would only surface rarely, who knows what can happen.

Over the years I’ve seen user comments at NewEgg describing exactly those sorts of experiences with various such enclosures, resulting in loss of all of the data.

@rbstehno had it right:

You always need a backup no matter what raid array you use or even if you spent over a million $$ on a disk subsystem.

Best regards,
-- Al

As someone who has a goodly amount of experience building my own very fast computers (which among other things I use for editing of 4K video material, which is a very challenging task for a computer), here are my thoughts:

I agree with @rbstehno that you don’t need speed. Also, given especially the need for a backup drive or drives I would choose a small number of large drives, rather than a multitude of smaller ones. And I don’t see any need for complicating things with RAID. Keep it simple!

What I would do is use a single 5400 rpm 10 TB drive for music storage, another 5400 rpm 10 TB (or larger) drive for backups, a self-powered external usb-connected 10 TB drive for a second backup, and something like a 7200 rpm 1 TB WD Gold drive as the system drive (i.e., the drive containing Windows and programs). (That’s more capacity than you’ll need for that drive, but I don’t think the Gold drives are available in smaller capacities). Or if you envision using the computer for unrelated purposes where a faster system drive may be desirable, consider a smaller SSD, perhaps even a Samsung M.2 2280 NVMe drive if your motherboard can support it, those being **extremely** fast.

To back up the music files I would periodically simply copy the files from the music storage drive to the other backup drives, telling Windows to skip files that are already there.

I would also consider using a disk imaging program to periodically create images of the system drive, storing the images on one or both of the backup drives. In the unlikely event of failure of the system drive that would avoid the necessity of having to reinstall and setup Windows and your programs. I suggest that you consider Terabyte Unlimited’s "Image for Windows" program, which I have used for many years with great results, or Acronis True Image, which seems to be fairly popular.

Finally, FWIW, my perception is that HGST drives (HGST now being a brand of WD) are not very popular these days, as evidenced in part by the limited number of reviews their recent drives seem to receive at NewEgg.com.

Good luck. Regards,
-- Al