What Are The Advantages Of Having Many DNS?

and also the disadvantages....?

[Mistra]

(1) What will happen if I sign up with a few web hosting companies in different continents e.g. 2 shared servers in USA, one shared server in South America, two shared servers in Europe, and one shared server in Asia to fill up the 13 slots given by Godaddy?

* Note: All my servers provide same static HTML content or dynamic content with same MySQL database that will not be updated.

(2) Does the DNS always choose the first nameserver that we keyed in at the domain registrar or does it randomly pick anyone?

(3) Will users in Asia be directed to the server in Asia or will they be randomly sent to any of the servers?

(4) Will it lessen the burden of my shared server if the shared server plan that I currently signed up with a hosting company couldn't handle the traffic?

Thanks for your answers.

[jtara]

First of all, there is no need to sign-up with multiple hosting companies on multiple continents in order to have multiple diverse DNS servers. There are companies that provide this service and already have an international network of DNS servers. And many of them do so at very reasonable cost.

13 is probably excessive.

The choice of webserver is "undefined". It is supposed to be random, but there are so many different implementations of resolvers and caching DNS servers out there that... who knows?

A better solution is to use a technology knows as IP Anycast. With IP Anycast, it's possible to have multiple DNS servers at the same address.

One of the most costly, high-reliability DNS services used by high-rollers uses only two "slots". But there are many DNS servers that answer to those two addresses.

Using IP Anycast - if properly implemented - your Asian users will be served by an Asian DNS server.

DNS traffic tends to be pretty small, due to caching. Unless you are running a mega-site, traffic is unlikely to be a problem.

Keep in mind that we are just talking about DNS here - NOT your web hosting! If you want your Asian users directed to a website in Asia - that is quite a different matter, which is neither as easy nor as affordable.

IP Anycast, unfortunately, works only for UDP packets such as are used for DNS - not for TCP packets such as are used for HTTP.

To actually serve content from a geographically-close server, there are schemes that combine IP Anycast technology for DNS, where DIFFERENT addresses are served by different DNS servers, typically also employing distributed load-balancing and/or caching HTTP servers. This is probably not a do-it-yourself project, unless you are an extreme techie with good connections (as in "who you know") to accomplish the routing.

There are companies that provide this service. For a pretty penny.

(p.s. I see that I misunderstood your original post, though I anticipated that you might have meant what you meant. :) Short answer: this isn't going to accomplish what you are trying to accomplish. with an IP-Anycast DNS solution, all the DNS servers are going to serve the SAME address for your web site. IP-Anycast, when applied strictly to DNS, simply increases reliability and decreases delay in looking up your site.

Many inexpensive DNS services provide load-balancing at the DNS level. They will round-robin requests to multiple servers. Instead of ONE address for example.com, you give them serveral. This might serve your needs. They don't take geography into account, though.)