>>Surely if you get to this stage then you may as well invest
>>is some proper dedicated high-availability servers with load
>>balancers? for each of your services!?
>
> Load balancing is not the problem ... the data needs to sync ... and
> these are mail servers, which makes it interesting ;)
Load balancing isn't just about connectivity, they are great for redundancy too
as you can bring servers up and down behind a load balancer without things
borking. HTTP is by the far the easiest as it is stateless but e-mail (IMAP,
POP3) and other protocols work fine too. The hard part is knowing where to stop...
Multiple ISP connections (multihomed)
into multiple firewalls
into multiple load balancers
into multiple mail servers
reading off multiple file servers
with multiple PSU's in each box
running from multiple mains feeds
... etc. etc. ... :-)
God, if only I had the money, I would love to play with this sort of stuff! :-)
Dan