This has been my system for a while now. The funny side is that, I have yet to have a drive failure so the amount of local backups is getting silly.
The other thing I did was I ended up collecting HDD's out of old DVR's people were throwing out. Those drives are used for cold storage but not for anything important because they already have tens of thousands of hours on them and in not the best temperature conditions. Again, non have failed yet.
Funnily enough, the only HDD I have failing is a 2.1GB Quantum Fireball from 1997 in my Pentium 1! Really should swap that for an SD card via IDE.
I've had drive failures now and then. I once dropped a 10T drive on the floor. I thoroughly examined it, and it was not only merely dead, it was really most sincerely dead!
A couple of years ago, I repaired one of a pair of drives (I think they were 750GB) that had the connectors mysteriously snapped off[1] while I was poking around in a client's system.
It was a special system, Linux-based, running proprietary software for expensive proprietary hardware.
I apologized profusely. I got them some new hard drives coming right away. I found a forgettable donor drive in the boneyard that had a close-enough footprint for the connector, harvested it with hot air, and put its connector onto one of the broken client drives.
A little bit of dd and some mdadm magic later, and they were back in business with that RAID-1 array like it never happened (other than just a few days of downtime on a system they only used occasionally).
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A different time, 25 or more years ago now, I somehow broke a 4-pin Molex[2] power connector off of one of my own IDE drives. I don't remember the details, but I do remember that I fixed it by soldering a Y cable power splitter into the holes on the board. This gave me a drive that worked, and that had power pass-through. It was kind of nice to have (and it worked for years and years after that).
Anyway, I guess shit happens sometimes.
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[1] I wasn't rough with anything; I was just moving wiring out of the way, as one does, to attack the dust bison that had accumulated over the previous decade or more with some canned air.
I somehow broke the connectors of both drives, anyway. I can't explain it and I don't have to, so I guess I won't bother trying. They were fine when I started and they were broken when I finished.
[2]: Those aren't Molex connectors. Everyone calls 'em that, like everyone calls adhesive bandages Band-Aids, but the old drives used a design characterized by the Amphenol Mate-N-Lok connector design which had nothing to do with Molex.
I've been programming for 50 years now. I've had all sorts of failures, including two incidents of my desktop computer burst into flames.
I now set the desktop on a piece of sheet steel. I also only use steel enclosures for them.
I have a Carver amp that runs 24/7 in my office, for the last 40 years. It's now emitting a 60 cycle hum, which I learned is due to decaying capacitors. I guess I need to get a cap kit and fix it.
Or just keep it attached to your system, so spyware, adware, and the NSA will make free backups for you!