[Freeswitch-users] FreeSWITCH HA + Loadbalancing

[David Knell]

On Sun, 2009-08-30 at 11:17 +0800, Steve Underwood wrote:
> This sounds like so many "redundancy" projects that will probably offer 
> nothing in the real world.
> 
> On 08/30/2009 05:52 AM, Pete Mueller wrote:
> > I guess I should also mention that Xen is a side-project.
> >
> > When considering this issue for an existing production systems, we 
> > chose to put as much HA into hardware as we can.  We are not concerned 
> > with FS crashing, as so far we've never seen that happen (except when 
> > our module caused it :)  So for each of our systems:
> > - We have dual NIC cards (onboad NIC + PCI card) both bridged together 
> > in case one fails
> NICs hardly ever fail. Its the wiring which is the vulnerable area. How 
> independent can you make the two wiring paths, when they come from the 
> same box?

This is one area where you can do quite well.  A simple setup:
two machines (1, 2), two NICs (A, B) in each, two switches (S1, S2)
- wire up 1A <-> S1 <-> 2A, 1B <-> S2 <-> 2B
- run OSPF across the links
allows you to unplug any cable or any switch without interrupting
communications for more than a second or two if the OSPF timers are
suitably set.

This generalises nicely - we used to run two machines as web servers,
each advertising the same IP address via OSPF to the routers via a setup
like the one above.  Unplug any one thing, and the whole still worked.

Three complete power outages in the data center we were in in 18 months,
one of which took out a number of power supplies, neatly illustrated
Steve's point: our real-world reliability was determined elsewhere.

--Dave

-- 
David Knell, Director, 3C Limited
T: +44 20 3298 2000
E: dave at 3c.co.uk
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