I have a PC I built as a nas, recently upgraded it to 4x8TB drives in raid 5, this gives me 24tb of storage as you lose one HDD to “parity” data but means a HDD can fail without data being lost.

This “hot copies” to an external 22tb drive overnight and does a full sync end of the week, so I have a local recovery for any data I may accidentally delete within a week. The 2tb smaller is just they didn’t do a 24tb drive at a reasonable price, figure by the time I get to needing the capacity one will be available to swap out to.

Everything is then backed up to a cloud storage service (backblaze, which is ridiculously cheap for unlimited data backups) and can order a drive with all the data on them in absolute worse case I need to recover everything and quickly, rather than waiting for however long it takes to download the 12tb I have with them currently. The service also has a year of file versioning to help against bit rot, if a file is corrupted I have a year with which to notice and grab a replacement from the cloud. They have unlimited versioning but with the amount of data I’m storing it’s a bit cost prohibitive to me.

All my photography is also sent to Amazon Photos (unlimited storage tier on my UK account, limited on my Aus account so your location may vary) - which I view as a free extra precaution given I’m already paying for prime for other reasons.

I’d like to upgrade to a better file system, like btrfs or zfs which will help prevent/ detect bit rot at the system level and be a tad more robust than the ntfs I currently use, but the system is a windows box to make it easy for my partner to also use where needed and going Linux to get these benefits has other knock on complications, badgering them in to windows has an air of unreliability, not something I’m comfortable risking on a storage system. So currently that’s my only risk, which is a low enough probability to not be a massive concern.