Load Balancing/Failover

[Derek Smith]

Hi,

We have two servers. One that will be servicing students requests, and one
that is a passive failover. What we want to do is create one Host record,
say portal.example.edu. We want the DNS server to point to the main server,
but in the event of a failure, have the DNS record point to the secondary
server. Is there a way to do this?

Thanks

 

[William Stacey [MVP]]

Just create two A records for the ownerName. One to HostA and one to HostB.
You can round-robin dns or not. If you do, then you will get traffic on
both Hosts. If the first host is down, the client (i.e. IE) will use the
second one. Not all clients will walk the A record list for next host, so I
guess that is app specific behavior. If you have two machines, there is
really not much sence in not using the second one or using it just as
backup. May as well get use out of it and round-robin your A records. HTH

 

[Jonathan de Boyne Pollard]

DS> Is there a way to do this?

No. The DNS is not a load balancing or a fault tolerance mechanism. It
is (amongst other things) merely a name->address mapping mechanism. To
achieve load balancing, you must operate in terms of IP datagram routing
or at the application level.

You may be told about round-robin resource record cycling. It often
comes up in response to questions like yours. However, "round-robin" is
not load balancing. It is a bodge that doesn't in fact achieve the
actual goals that people want to achieve. It doesn't achieve either
load balancing or fault tolerance.