Re: failover and dns

["Steven W. Engle" <sengle () dhtinc com>]

> Dear All,
[snip]
> Company A now wants to improve resilliance. The have datacenters in
> three
> continents and so the basic idea is to put up three copies. Now the dns
> entry will
> point to one of them, if that fails then the contents of the dns will be
> changed (not
> by hand) to point at the secondary etc. Use a very short ttl on the dns
> entry and
> things should start again after a short while.

It strikes me that a round-robin DNS might serve you well here. To my
knowledge, round-robin DNS won't handle "if A fails then try B" -- it will
cycle through all 'X' datacenters/sites, distributing the connections
amoung them. In this scenario, if a particular site is not available, the
user would have to try again later and most likely (with a short TTL) get
sent to another site.

Are there round-robin DNS implementations that perform "aliveness" tests
and drops unavailable sites out of the round-robin?

--
Steven W. Engle                          Voice: (281) 333-9085
Diversified High Technologies, Inc.        Fax: (281) 333-9087
1350 Nasa Road One, Suite 105           http://www.dhtinc.com/
Houston, TX  77058                    mailto:sengle () dhtinc com