once some one was saying , to specify separate name servers for the backup website and it your main host is dead the other host will be picked up from name servers...am not sure is it right to do or not
I tend to keep all three points of failure isolated. I register the domain via NS. I use a third-party to handle my DNS. And different companies for my production and backup sites. Some might call that paranoid. I call it good advice based on over a decade of experience. Of course if NS dies the rest is pretty much useless. But if NS dies I suspect the internet, or at least sites in the US, would be pretty much useless since so many people register their domains through them despite the prevalence of discount registrars.