[asterisk-users] Problems with the voice quality under load

[Mordechay Kaganer]

B.H.

Hello, all :-)

We have a cluster of Asterisk (v. 11.9) servers that host IVR applications.
The servers work behind SIP proxy (kamailio) for load balancing.

All servers are in 2 processor configuration, 8-10 cores per CPU.

When a particular server gets about 500 concurrent calls, the sound quality
begins to degrade, the sound plays slowly and with clicks. As far as i
understand, it's because asterisk is unable to send the voice stream in
time i.e. the server is overloaded.

What i don't understand is, at the time that the server appears to be
overloaded and the audio quality is bad, actual server's load is no more
than 30-40% (60-70% idle CPU on average). IMHO, this indicates that for
some reason the server is unable to use it's CPU capacity efficiently. May
be because of some kind of thread contention inside asterisk?

I have read blogs that advice to divide physical server into several VMs
and they claim that this will improve the total capacity. In my own
experience, this did not work very well and seems like the visualization
actually made the quality worse.

Do you have any advice for me (other than purchasing more servers ;-) ?

Thanks!

-- 
משיח NOW!
Moshiach is coming very soon, prepare yourself!
יחי אדוננו מורינו ורבינו מלך המשיח לעולם ועד!
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