As a simple hobbyist I just use regular HDD's as backup media, and put them in simple commercially available silicone sleeves. I don't go throwing these things around and never had an issue with them.
If I was more serious, I'd make some kind of padded suitcase (or two) and put a full HDD with it's silicone condom in an ESD bag with some dessicant and seal it hermetically with such a kitchen bag sealer, and add a 3rd layer to prevent the water & moisture barrier from getting small punctures from grains of sand and such.
For a long, long time HDD heads are parked with the heads lifted from the disk and are quite robust, but they do have a limit on G-forces.
Yes, and these can be exceeded by a simple drop. On some drives the robustness even depends on which side the drop is.
Hard Drives are certainly a good option for hobbyist use but they can't compete with the robustness and reliability of LTO cartridges.
Price of HDD storage is also similar to tapes, but you don't need an extra tape drive.
That really depends on the amount of data you want to offload.
For example, I can buy new LTO-5 (1.5TB/3TB) cartridges for approx $30, and that gives me approx 2.2TB of usable capacity. A LTO-7 (6TB/9TB) cartridge is $80, and with the data we have I get over 8TB on one. An LTO-8 (12TB/30TB cartridge) I can get for approx $100, and that gives me more than 25TB on storage.
While I can get new 2TB drives for $50, I haven't seen any 8TB drive for anywhere near $80.
Of course the tape drive itself is pretty expensive (around $2k for an LTO-7 drive and around $3k for an LTO-8 drive) but the more data there is to store the cheaper the tape becomes over HDD.
Then there's the transfer rate. Even fast SATA hard drives max out at around 200MB/s, and sustained the rate drops even further (often below 100MB/s). SMR drives (which are spreading at the lower cost end of the HDD market) can drop even further (<30MB/s). In comparison, LTO-5 streams at 280MB/s sustained, and LTO-7/8 can go up to over 700MB/s sustained (which is more than what the fastest SATA SSDs can achieve as peak rate!).
As backups are all about redundancy, have you considered using both?
Relying on a single backup is completely bonkers with today's storage prices. If a HDD with any of my backups fails, I open it for the magnets, bend the disk (or cut first surface mirrors out of them) and grab another HDD with data.
I agree, a proper backup strategy is important independent of the medium.
For me, I also used old left over HDD's. For a more serious Backup I would not. Best is probably to use a HDD for a few months, to weed out early fails, and after that only use it for backup to reduce bearing wear.
A friend of mine one had a HDD that failed to start (this was in the '90ies), and I helped him by holding it in my hand and rotating it back and forth so the inertia of the disks gave it an exta jollt to overcome the increased friction. Then of course we proceeded to backup that drive and it was the last time it was used. These day's you monitor the SMART data.
Well, hard drives do still fail sporadically, or sometimes even without SMART warnings. At least bearing issues are mostly gone thanks to the move to FDBs some 15 years ago (although they can potentially dry out if stored for a long period of time).