All Metal too! I don’t have a use for them right now but I’m sure I’ll find out something! (I have 14 of them…)
Secondhand stuff can be really cheap if you know where to look, but the drawbacks are usually power and noise.
Especially for hard drives. 8TB SAS drives are down to about $45 a piece.
Brand new enterprise-grade 8TB drives are more around $180 new. Meaning as long as you have redundancy (which you should anyway) then you can lose four used drives before it stops being worth it. Not to mention drives get cheaper so if your $45 drive dies 2 years from now you could probably replace it for $35 etc.
Just buy them on eBay. Why does it matter where they come from? Again, four of them have to die before it’s no longer worth it. It’s extremely unlikely you’d be that unlucky.
Personally I have 15 drives in my NAS, all of them were bought used and they’ve been running 24/7 for 4+ years without issue. Originally I expected to lose at least one per year but they just keep chugging along. All of them have at least 40k power on hours, with the oldest 3TB ones having over 80k (9+ years)
I use unRAID so if/when one does die it’s as simple as pulling out the dead one, popping in a new one, and letting it rebuild itself.