Do resolv.conf:
Up to MAXNS (currently 3) name servers may be listed, one per
line. If there are multiple servers, the resolver library
queries them in the order listed. If no nameserver entries
are present, the default is to use the name server on the
local machine. (The algorithm used is to try a name server,
and if the query times out, try the next, until out of name
servers, then repeat trying all name servers until a maximum
number of retries are performed.)
Once all the nameservers are tried, and the query fails the default is
to return the host not found message.
Can you repeat the same line below in the conf file so that multiple
nameserver
directives are added. Each line of nameserver
directive
supports upto 3 DNS addresses (per line).
Please note that only one host is ever tried, and that is on the top
of the list in resolv.conf; if the address is not found on the first
server or the server is not reachable, and only then the second is
tried and then continues for the third server if the query on the
second server fails. There is no round-robin or random selection of
nameservers from resolv.conf during the host resolution, so the cost
of trying all the nameservers will be directly taxing on the
performance of underlying systems/applications.
No entanto, acho melhor implementar um servidor de nomes de cache local, o aumento no desempenho do DNS para aplicativos usando / dependendo da resolução do host aumentaria se o número de chamadas de DNS fosse reduzido / dependesse da latência também.
Outra abordagem seria usar servidores openDNS, eles talvez tenham os servidores DNS mais atualizados e também rápidos na Internet.