Do I need to be concerned about DNS server reliability?

[musicales]

I confess I'm not entirely clear how the whole DNS architecture works, but after years using the DNS server of my host I just discovered I can set the DNS with the company I buy the domain names from.

What I wanted to know was if I do use the domain name company am I doubling the risk in terms of their server going down (as well as the risk of my hosting company having a problem), and is their any issue with such companies in terms of bandwidth/usage if I have a particularly busy site?

[kalos]

I'd just ask them for uptime statistics on both servers (DNS, Web). Do they offer an uptime guarantee (usually >95%, with 99% preferred as no one can hit 100%). No service provider should charge you for bandwidth when hosting your DNS entries. They may charge you to host them, but it's a nominal fee and for the life of your contract.

-ben

[lammert]

I would not go for 95%, or even 99%. 95% means that the host is offline for 18 days each year, 99% is still more than 3 days. Most decent companies offer 99,9% which is still 9 hours down time per year.

[jdMorgan]

Remember that the DNS system is distributed; The browser of a visitor to your site gets the IP address of your site from the visitor's ISP's DNS server. If that DNS server doesn't have the translation, then it gets it from the DNS server above it (for example, at the backbone level). The DNS server you control is the "authoritative" DNS server for your domain. But it is only accessed if a lower-level DNS server does not already have an unexpired copy of the domain-to-IP translation. Therefore, the system is fairly fault-tolerant, as long as you don't set the expiry period (DNS TTL) too short.

Jim

[musicales]

jd - I think that's the answer I was after. Many thanks