I have a 4tb HDD which I use as a nas drive. Should I add another 4tb and use it as raid 1 . I don't have any more storage to have any backup. Is it better to periodically backup to a new drive than setting it up as raid 1. Open to suggusions .I only have one 4TB drive as of now. And its 4years old. I know my data is at risk. 3-2-1 backup is not affortable. But I don't care about downtime if any drive fail . So what is the cheapest way to have some data backup.