[Linux-cluster] High availability mail server

[Madison Kelly]

Samer ITS wrote:
> Dears
> 
>  
> 
> I have 4 servers. And I need to install high availability mail system 
> (Postfix, Dovect, Spam, mailscanner, ….)
> 
>  
> 
> Best regards

Hi Damer,

   Hi have to agree with Finnur, if in idea and not tone. :)

   Clustering is not very easy. It is complex and, as I've learned 
myself over and over while learning it, it is very easy to break. You 
need to understand how all the parts tie together so that when you do 
need to change something, you know how the other components will react. 
There is no simple canned solution around this -- It's just too small a 
segment of users.

   Answer these questions;

a) What if your goal with clustering? Performance? Uptime? Scalability?

b) These four servers, do they have mechanisms for fencing like IPMI 
control boards?

c) Do you understand terms like Heartbeat, Cluster-aware file systems, 
iSCSI/SAN/NAS, Fencing, Split-breain, Quorum?

d) What operating system and what cluster tools do you plan to/want to use?

   I'm not trying to discourage you from clustering, honestly. I am, 
however, trying to keep you from getting in way over your head. I've 
been playing with clustering for a couple years now and I still 
constantly run into issues for no other reason than that I simply didn't 
understand the systems well enough.

   As for your specific application; Have you though about how you are 
going to handle user authentication? Will you need to support multiple 
domains?

   You have a *lot* of variables you need to sort out in the mail system 
alone before you can start worrying about the cluster component.

   If you have a short time line to launch, hire a consultant who is 
already familiar with clustering. If you have lots of time, start 
reading and then come back here with specific questions, including steps 
you've tried, specific errors you've run into and so on. You will find 
this list very helpful when you show that you've put some effort into 
your system already.

Best of luck!

Madi