Dns-operations mailing list

[Falk Husemann <josen AT paketsequenz.de>]

Moin,

On 16.05.2012 21:36, Alex Hanselka wrote:
> Possible. I know there are some issues with DNS running masked like that. I 
> think Jeff has more info on the matter.
> On May 16, 2012, at 2:35 PM, Jonathan wrote:
> > Maybe something like this
> > http://kb.linuxvirtualserver.org/wiki/IPVS


what is the benefit of running it? You need one load-balancer with one 
IP that forwards the request to the nameserver and the response to the 
client.

There are three operation modes in LVS, which all three don't provide a 
benefit for availability from my point of view:

Lets suppose we have four servers. A to C are our nameservers, Z is the 
LVS running load-balancer.

LVS/NAT:
Every request to Z is sent to one or more of A to C, the answer is sent 
to Z and from there to the client.

LVS/TUN:
Every request to Z is sent to one or more of A to C, the answer is 
routed to the client through Z (like VPN).

LVS/DR:
Every request to Z is rewritten to one or more of A to C by ARP, the 
answer is sent to the client by posing as Z via ARP.

All in all, if Z goes down, the cluster is not working. As LVS is meant 
for distributing taxing requests computewise, it doesnt solve the 
Single-Point-of-Failure Problem. Only Anycast does this. In this example 
it would provide even better latency to just stop worrying and start 
loving DNS on Z ;-)

Falk