Help can someone ssd have 2 512gb ssd want one for backup and have 1hdd 16tb -- 2

Please elaborate more about the issue. I have trouble understanding the actual scope. Please describe using more words.

I can do this using software raid or if you have a raid card it would be faster the two ssds will be in raid 1 and the hdd won't be in raid so as I understood you don't want to back up the hdd, this will make sure if one ssd fails the other will work, but this isn't full back up as it won't work if you deleted a file, there is another way which involves cloning the drive every week/month/time you boot/on command this depends on your need. I can do both ways which ever is best for you use case