Re: virtual_server_group does that do what I think it does?

On Thursday 24 July 2014 10:59:53 Mike Williams wrote:
> On Wednesday 23 July 2014 10:45:55 Todd Fleisher wrote:
> > I use this feature extensively and can hopefully help you understand 
with
> > an
> > example:
> I need an actual light above my head, that goes 'bing!'
> Because I just got virtual_server_group!
> 
> 
> The key bit of information I was missing was you define one 
virtual_server
> and put multiple VIPs in a virtual_server_group, keepalived expands 
that
> into multiple virtual_servers.
> 
> On one test system the number of checks has gone from 35 per 
minute to 2.
> The config also went from 3117 lines to 587.

What you will still have with this approach - have a look with "ipvsadm -
Ln" - is a separate kernel IPVS level virtual server for each of the VIPs, 
each with a separate set of (same IP/port) real servers in it.

There will be some overhead when real servers need to be modified 
(because they broke or get well again), as keepalived has to modify 
them once for each separate IPVS level virtual server. Probably no grave 
problem.

But this especially also means that round-robin / least-connection 
scheduling happens separately for each VIP, not taking into account 
connections to same the real server, but through a different VIP.

Depending on your needs, that may be irrelevant, desired, or 
problematic.

Using the single-firewall-mark based approach, circumvents both 
issues, as there really is only a single entry for each realserver - but at 
the permanent cost of running iptables rules for the classification 
(which can be hugely reduced by using ipset matches, btw)

best regards
  Patrick

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