How much data are we talking about? I get confused. Is it 1.5TB or is it 2.5TB?
Then, how backed up do you want to be? Think about if you REALLY need daily backups. While Raid might be cool and flashy; if you don’t need it you don’t need it and running it only creates cost.

If you have about 2 TB of data then i would just buy 3 external HDD of 2TB size and replace them every 5 Years. Then rotate them around every time you do a backup. Can you automate your backups? Not to the point of you not having to do anything. Unless you choose to pay for 2 cloud storage providers and both offer you to save your backups in an unchangeable state.

I really love Kopia.

I mostly use it for cloud backups but it also works great for local/network storage as well.

It’s really fast and efficient, supports cutting edge encryption and compression algorithms and the de-duplication and file-splitting features will let you generate frequent snapshots while costing you minimal storage.

Snapshots are also effortless to mount and it even supports error correction to protect against bit-flipping and other long-term storage risks.

It’s also cross-platform and FOSS.

De-duplication prevents duplicate bits of data from being stored twice. Even if they are different file names or even synced from different systems.

The rolling hash/file-splitting means if you modify a 25GB file and only change a couple MB then only the changed couple MB will need to be stored. This means you can spend a month modifying small parts of a massive file thousands of times and avoid storing a new 25GB file thousands of times to archive those changes.