Re: question about transparancy

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 :)
>>

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..

-- 


With kind regards,


Angelo Höngens
systems administrator

MCSE on Windows 2003
MCSE on Windows 2000
MS Small Business Specialist
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