Nextcloud can easily handle 4Tb, I've seen guys with 50Tb instances with no issues

The backup problem is eternal. If you can, set up a consumer NAS somewhere else than where your server is and back up daily to it. Even over a slow connection, you should be able to get by after the first full backup.

If you can't do that, either you go without backups and learn the hard way when your systems fail (I'm currently doing that, still waiting on the find out phase), or you will have to pay someone to store your data somewhere. From what I hear backblaze is affordable, but they do charge you per download. For 4 Tb, they would charge $180/year, with added costs per download which hopefully you can avoid.

A final alternative is to store cold backups somewhere else (at work, for example). Buy 2 external disks, and back up your server to one of them. Store it at work, then do the same with the other disk. Every month, rotate the disks. Your backup solution probably has a function to do exactly that, so you can leave one plugged in, accumulating this months data over time.

I haven’t noticed anyone else bring it up, but you mentioned in passing the possibility of using a RAID 0. I’d avoid that except in very specific circumstances. They’re potentially fine for a scratch disk type of scenario, but if any member of the array fails, the whole array is toast. The chances of a failure increases with was each disk added, so a RAID 0 is less reliable than a single disk. I definitely wouldn’t want to trust my family’s photos to it.

I run 120TB on a VM with 2 cores and 2gb of ram. Data storage is not very hardware intensive. Now serving the data to dozens of users is where you're going to have issues.

I backup to Backblaze B2 (6$/TB a month), but I have much less data. I also backup all my data to another disk that lives in the same server. Id probably continue doing manual backups to external drive due to the cost of cloud backups

You'll have an hard time with Nextcloud for that amount of files and total size. If you plan to sync better pick up something better such as Syncthing as it is robust, it doesn’t fail and handles tons of files with little resources, NC uses a lot more RAM and once you get to around 1 TB of small files it will stop working randomly.

If you just want a simple webUI to browser your files I would pick FileBrowser because it is very reliable and easy to setup. You can easily combine FileBrowser and Syncthing to have a cloud-like experience as well.

i think nextcloud will work perfectly fine.

for backups you can either have a secondary server at a relative's home (use syncthing for syncing files) or go for a dedicated server, hetzner is pretty cheap.

Sorry for my bad English btw

Cloud question:

Hetzner Storage Boxes.

Supports Snapshots. Create one every Day the last 30 days. Ez way to have another way of rolling back older backups.

Got 10TB available for ~24€.

Sync up there with rSync Protocol.

To be fair I am backing up from a Synology NAS so I am playing this in EZ-Mode :D

Don't know how easy this is to setup on nextcloud.