-------- Original Message --------
Subject: Re: question about transparancy
From: Angelo Höngens <a.hong...@netmatch.nl>
To: haproxy@formilux.org
Date: 04/23/2010 11:31 AM
On 23-4-2010 11:19, Michiel van Es wrote:
Angelo Höngens wrote:
On 22-4-2010 20:28, Michiel van Es wrote:
Yes
That is the default smtp failover setup but I want to balance the load
via a load balancer setup
Mx records can not balance load
If you have 2 mx records with the same priority, your load should be
balanced..
Or you could have a single mx record pointing to a hostname which has 2
A records.. DNS round robin will take care of the balancing.
That is why there are almost no smtp balancers, because it is not
needed. In the 1980's they already designed smtp for balancing and
failover. For other protocols this was not so easy, that's why people
wrote http balancers :)
Yes I understand, but what about settings features as weight or doe
advanced load balancing?
You can't do advanced balancing, true..
If you *must* have weight, you could go for the host records approach.
Make 1 MX record pointing to mx-in.example.com, and create three host
records: mx-in -> x.x.x.1, mx-in -> x.x.x.1, mx-in -> x.x.x.2. This way,
server 1 gets around 66% of the sessions, and server 2 gets around 33%
of the sessions.
What is one of the mailservers are broken and you want to take it offline.
With a normal TTL in dns it can take 1 or 2 days before other
mailservers know it should not send a mail to that server and use the other.
I like load balancers because they can let you decide how traffic must flow.
No problem if you use the MX way, just take the server offline, no need
to change dns.. Remote mail servers will just try one mail server, and
if it's down, they will use the other, failover is built into the way
smtp and dns work together.
I'm not saying you should not do what you are doing. If you really want
to use your own balancer, and you feel better doing that, then by all
means please do. What's I'm saying is that people have been balancing
smtp servers for 30 years using the ways they though of in the 80's, and
since that works for most organisations, it might work for you. KISS.
Don't look blindly at the tools you're using, but choose the tools you
need based on the goal you're trying to reach. Ah, who am I kidding, I'm
just an IT-nerd wanting to play with cool balancers as well..
That is the whole idea ;)
I know DNS load balancing works (I have it up & running right now) but I
want to do load balancing with a load balancer..I want to have a setup
which is flexible and a blueprint for let say: a 500+ mailserver setup
with very heavy load (think Google or Hotmail).
Michiel
