PETG is food safe. However! Because FDM is full of gaps, cracks, and voids, NEVER use it to store food that can spoil. Food bits can get trapped in these voids and present a persistent risk for foodbourne illness.
Granulated sugar would be fine if it's kept very dry, however do note that said voids will not make an airtight container. So I wouldn't even use it for stuff affected by humidity or oxygen.
If anything I'd almost suggest clearing the inside with a food safe platinum silicone, which should solve most of these issues.
Raid1 that thing and sleep easier. Good on you for having a cold spare, and knowing to buy your drives at different locations/times to get different batches. Your head is in the right place! No reason to leave that data unprotected if you have the underlying tech and hardware.
This is called overrun and is the main way you get shorted on product. More overrun means a creamier feeling product, but it also means you get less. So there's that.
All of this stuff is usually fit onto a single board, crammed into a very specific amount of space, and is thoroughly and iterated until it works properly. This isn't the kind of stuff a home lab does, but you could certainly try. I think it would be damn near impossible to do it better and more reliably than teams of hundreds or thousands of various engineers. It's not like you can just take a phone CPU and slap it on a random board without a ton of forethought.
PETG is food safe. However! Because FDM is full of gaps, cracks, and voids, NEVER use it to store food that can spoil. Food bits can get trapped in these voids and present a persistent risk for foodbourne illness.
Granulated sugar would be fine if it's kept very dry, however do note that said voids will not make an airtight container. So I wouldn't even use it for stuff affected by humidity or oxygen.
If anything I'd almost suggest clearing the inside with a food safe platinum silicone, which should solve most of these issues.