[asterisk-users] RE: Scaling Asterisk: Dual-Core CPUs not yielding gains at high call volumes

[JR Richardson]

> >   In fact, it seems that somewhere between 200 and 300 calls, the two
> > servers start to exhibit similar idle times despite one of them having
> > twice as many cores.
> >
> 
> Sounds like you are running into the hardware limitations of your
> systems PCI or "Front Side Bus" (FSB) and not necessarily an issue of
> asterisk.  In short there is a limited amount of bandwidth on the
> computer's PCI Bus (33 MHz)  and the FSB (100-800MHz).  One thing to
> remember is that ALL cores and data streams need to share the PCI and
> FSB.    Asterisk is very processor and memory intensive.  At the extreme
> level of usage more cores won't help if data is "stuck in the pipe".  So
> the performance planing you described would be expected.
> 
This is a great point.  FSB speed has always been a bottleneck in relations
to PCI and Proc speed increases.

The Dual-Core system you are working with must have cost a bundle, several
thousand.  My approach has been to stick with single cpu, single core
servers and add more servers to the cluster, versus building bigger, faster
Proc servers. With sub $1000 servers, I can achieve 150-200 calls per
server, cluster several servers together and for the same price as a quad
proc dual-core server have 700-1000 call capacity.

Now, with that said, a cluster becomes harder to build and operate than a 1
server Asterisk implementation and does not work well in some environments,
such as with large call queues.  But when you are talking straight call
capacity, multiple servers will usually dominate singe servers in relation
to cost.

All,

Nice discussion, and thanks for posting your benchmark results and feedback.

JR
-- 
JR Richardson
Engineering for the Masses