Herbert Poetzl wrote:
>>> The scenario is this:
>>>
>>> I have a load balanacer (lb) sitting in front of some servers, one of
>>> which is a vserver host. One of the load balanced services is mail, and
>>> it has the virtual IP of 4.3.2.1 on lb. The vserver host contains 2
>>> vservers: one for web with ip 1.2.3.4 and one for mail with ip 1.2.3.5.
>>> There is a separate mail server with ip 1.2.3.6. Mail traffic coming to
>>> the ip 4.3.2.1 gets distributed between 1.2.3.5 and 1.2.4.6. These
>>> servers need to have a hidden interface with the ip 4.3.2.1 so that they
>>> accept the packets forwarded by lb.
>>>
>
>
>> I am just trying to work out a way of getting vservers to work with our
>> existing load balancing setup. If we call the IPs for services on the
>> load balancer "virtual" and the machines actually providing those
>> services "real", then our current setup requires that the virtual IP
>> from the load balancer also exists on the real server on a private (not
>> responding the arps) interface. This is the equivalent of
>> http://www.linuxvirtualserver.org/VS-DRouting.html.
>>
>
> assuming the description given above is accurate, the
> problems you try to solve are like this (correct me if
> I'm wrong)
>
> - mail server A (192.168.1.25) on the Host X
> - mail server B (192.168.2.25) on a separate Machine (Y)
> - web server (192.168.1.80) on the same Host X
> - load balancer which uses 10.0.0.25 for both mail servers
> (separate hardware, not on Host, Z)
>
> and the web server, should use the 10.0.0.25 to reach
> _a_ mail server, which will be decided by the load balancer
> (could be 192.168.1.25 or 192.168.2.25)
>
Yes, this is more or less the end result.
> IMHO, to achieve this, only a few things are necessary:
>
> - assign the 10.0.0.25 IP to the loadbalancer
> - assign the 192.168.x.25 ips to the mail servers
> - have the web server use the 10.0.0.25 IP
> - have the load balancer distribute (and of course
> track and NAT) 10.0.0.25 to the 192.168.x.25 ips
>
> so, this doesn't involve any special setup on the Host
> (Linux-VServer or network wise) to get the desired effect,
> unless, you want to put the load balancer on the same
> Host, which makes it a different game to play ...
>
> please try to describe the problem in more detail,
> and/or try to give some arguments for this specific
> setup, whatever it might be ...
>
>
Yes, this is one way to do it. However, with load balancing there are
two mains way of doing traffic:
1) NAT where you NAT all the traffic back through the load balancer
2) DSR (Direct server return) where you route incoming traffic through
the load balancer and route outbound traffic through a router directly
back to the customer.
DSR is what we currently have setup and what I was trying to replicate
in a vserver environment.
The advantages of DSR are that with most of the traffic you would load
balance (HTTP, IMAP, POP3) there is more outbound traffic from the
servers than inbound. Therefore with the NAT method you are sooner
limited by the throughput of your load balancer due to it having to
handle the outbound traffic as well. Also, you can become limited by the
number of NAT connections your load balancer can handle.
That said, I'm going to see if we can handle our load using NAT since
there doesn't seem to be any way to get DSR working with vservers.
Jeff
Received on Mon Sep 3 01:59:30 2007