|
Omar Armas wrote:
Hi, I want to set up a farm of mail servers with load balancing.
Which method is the best under the following conditions:
-Services load balanced: SMTP, POP and IMAP.
-3 nodes initially and growth to 5 or 6 nodes in a few weeks. may more
come later.
-Linux (Qmail-LDAP as MTA)
Which method for load balancing would be best for this? DR, NAT, TUN?
I have a LVS/DR for HTTP, and remember to have read that LVS/NAT doesn´t
scale very well with large installations. Is that true? Is it solved?
What about tunneling?
DR will scale the best. In a NAT configuration all the return traffic
from the nodes has to pass back through the LVS. In a DR configuration the
nodes themselves respond to the client. There is nothing to solve in
the NAT configuration because nothing is broken. NAT by it's very nature
just doesn't scale well.
Is LVS/DR the only in which nodes have to be Linux? For what I´ve read,
in NAT and TUN I can use other OS(FreeBSD), is that right?
No. You can have whatever OS that has the capability to ignore ARPS.
FreeBSD nodes in DR configuration work fine you just need to use the
-arp flag with ifconfig. I believe you can even use Windows as a node
if you so desire. Never tried it but I don't see a reason why it would
not work.
Steve
| 