A "what if" scenario for Name Servers

[Ulysses]

G'day,

I have encountered the following negative argument for running DNS servers from the same box, by a competitor, who constantly uses this argument to scare customers away from other hosts, presumably to him. Is it true? Here it is:

The whole reason why you are FORCED to specify 2 name servers is to prevent DNS cache records from expiring and then caching a DNS failure.

The way it works is this:
An ISPs TTL (time to live) for a particular domain will expire, the ISPs DNS server then queries the name servers set for the domain to obtain an updated TTL and A record for the domain.

X ISPs DNS server will query ns1.something.com (whatever is specified for the domain in question). If that times out, it will query ns2.something.com and so on until it runs out of name servers to query.

If all of the name servers specified for a domain time out, the domain will be cached as non-responsive (poisoned) on X ISPs DNS server so that bandwidth / processing power is not wasted continually trying to query failed name servers.

When the name servers finally do come back online, the ISP still won’t query those name servers until the poisoned cache expires – a time which is defined by each ISP.

The net result is that the name servers and host server (in this case all on the same box) can be online, while ISPs will return poisoned cache results to the client – so the site will still look down even though the host is up.

Running DNS servers even from the same network is a VERY bad idea. Running DNS servers from the same box is…suicide.Is any of this correct? If it is, is it really a "suicidal" problem?

No hurry guys, but I'd really like to get around this argument - and "outsmart" this bloke. :cool:

Michael

[charles]

Hi Michael

There is nothing fundamentaly wrong he is telling you, but I don't consider it suicide.

Yes, it's better to have your DNS servers on seperate servers and seperate networks, but the tradeoff in price and managability, and the fact that literaly millions of people do this successfully make it a pragmatic and feasable approach.

We only offer VPS in one datacenter (right now), but our BGP network ensures you'll never have a network outage long enough to cause the dns servers to not be available for long. We offer a lower end $25/month VPS thats ideal for a dns server and DNS clustering is trivial to do with cpanel. Once we offer VPS out of more than one datacenter this will become doable in a cost effective manner.

Until then, if you you want enterprise class redundency then you will need to pay a little more than a VPS costs. Please send an email to sales@defenderhosting.com if you want to rent dedicated servers in our San Jose, Chicago and Viginia Equinix facilities for true redundancy. It's not going to be cheap.

charles

[Ulysses]

Thanks Charles,

As I now understand it, the probability of such an event actually occuring is so remote, that the benefit of the solution is negated by its costs. And from my point of view, where the technical support is as good as yours is, I have no concerns whatsoever.

Thanks again.

Michael

[jpetrov]

As Charles said - you either do it the expensive way (i.e. setup load balanced and failover servers in more US locations + Europe + Asia - not only for DNS) or you do it the cheaper way. The benefit of VPS is that it can be up from the backup in a relatively short time...