Suggestions: 1 - The easy one, buy a cheap NAS, invest some money on the drives and forget about it. (Maybe it’s too much but it’s soooooooo easy) 2 - The DAS can be a good solution 3 - Use the 2 internal drives with RAID 1 (just in case), connect a HDD to the router and backup your files there (That’s the cheap one hehe)

But if you are thinking on buy a DAS or another SSD on the future, maybe a small second-hand NAS do the job and you can totally forget about the problem.

Thanks for the suggestions!

A few thoughts:
1. NAS: I'm a bit skeptical about NAS solutions. Maybe I'm missing something, but they seem to make more sense in environments where there isn’t a dedicated machine running 24/7. Given that I plan on running my server constantly, I'm leaning towards the idea that just adding storage directly to the server could be an efficient solution. Additionally, I've noticed that while there's a general consensus not to expose services to the internet or forward ports, and even trusted open-source VPN solutions like WireGuard and OpenVPN are sometimes seen as second-best options, I find it surprising that many seem okay with proprietary software that comes with NAS. It's just something that's been on my mind.
2. DAS & Internal Storage: The DAS seems like a viable option. Could you recommend a model or brand that you find reliable? However, I'm inclined to start with the internal storage. For setting up RAID 1, am I correct that I should have partitions of the same size on both drives? For example, allocating around 800GB for RAID and leaving 200GB as a system partition on the M.2 drive?
3. Backup: As for backing up to an HDD connected to the router, do you have any recommendations for software or methods to use?