off-site slave servers? advice?

[Kevin Darcy]

loren jan wilson wrote:

>On Thu, Jul 01, 2004 at 03:27:58PM -0400, Barry Margolin wrote:
>  
>
>>I can imagine problems that would occur if one of the servers is 
>>responding *incorrectly*, since this might not trigger failover.  
>>Different nameserver implementations do indeed have different criteria 
>>for when to try another nameserver if they get a failure response from 
>>the first one.
>>
>>But if one of the servers simply stops responding, failover should 
>>always occur.  That's the whole point of listing multiple nameservers: 
>>to provide redundancy when nameservers or networks fail.
>>    
>>
>
>I understand, but since we moved to bind 9, that hasn't been the
>case. A good example is what we went through with the .cn (china)
>domain last month...we lost network connectivity to parts of 
>china, and users started complaining that chinese websites stopped
>coming up. We checked, and it turned out that our nameservers were
>having intermittent difficulties resolving hosts in china, even though
>we could get to some the webservers by ip. This condition stayed the
>length of the outage, which was over a week.
>
>Can anybody else make a statement that would clarify matters?
>When we first upgraded (over a year ago), I asked the bind 9 list
>why we couldn't resolve a particular domain all of a sudden,
>and somebody answered by pointing out that one of the domains'
>nameservers wasn't responding to queries. I understand that it's
>supposed to break if the nameservers don't respond identically
>for a domain, but why does it seem to break when one of the nameservers
>goes down?
>
One nameserver going down does not cause this behavior. We've had single 
nameservers go down from time to time and the whole DNS infrastructure 
doesn't go south. Now, if *all* nameservers for a particular domain go 
down, then that's a problem. Were all of the nameservers for the Chinese 
domain on the same network?

Having said that, diversity is of course a good thing.

- Kevin