A RAID1 array of 2 x 8TB SSD suffice (e.g. Samsung 870 QVO 8TB).
Your server can accommodate this.
When it comes to upgrading the server, to prevent downtime you could set up a new server with this configuration alongside your existing server, and migrate the data to the server at your own convenience. If you can afford to have an overlap of two servers running at the same time, this will save a lot of stress.
If you're not constantly writing-deleting-writing-deleting to the database, you do not necessarily need an enterprise SSD. An enterprise SSD is better suited to servers that write to disk dynamically. If you are just writing data and leaving it, the consumer grade SSDs will do fine.
But ultimately, it depends on how your database operates.
A RAID1 array will write the same data to both disks, so the one drive backs up the other. If one drive fails, the other one will still be alive (and so will your data), and you can replace the broken drive.
But, just because the one drive backs up the other, it doesn't mean your data is "backed up". If the server room catches fire, both of your hard drives are in flames in one flaming incident. So you still need an actual back up plan in place: like downloading the data to a server/laptop in another location.
You can rent a cheap "HDD Storage VPS" to help with backups if you need to.
But yes, 2 x 8TB consumer SSDs in a RAID1 away will achieve your goals of 8TB storage with an added layer of redundancy.
Just remember to backup your data.
