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I have Asterisk running on an Amazon M1 small instance. The maximum number of lines do not exceed 20.

After running for awhile, voice quality decreased. Some noises appear and voice was getting interrupted. Most likely, there were some issues with the network or CPU. I can see that average CPU usage is about 50%.

M1 Small instances have only 1 core and 1 computing unit. I'm not quite sure what is the root cause of the problem. Should I consider upgrading the Amazon instance to a High-CPU instance?

Can 50% CPU usage affect voice quality?

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  • If you're only seeing 50% CPU utilization, then you are not CPU bound and moving to a faster CPU without changing anything else won't change anything except lower your relative CPU utilization.
    – user
    Nov 16, 2013 at 22:22
  • Have you checked packet loss? Rung ping google.com and let it run 100 times. Look for drops or a % packet loss. Do this on the Asterisk box as well as the client network, if possible. The noises you hear could be those dropped packets...
    – jmort253
    Nov 16, 2013 at 23:00

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When you run asterisk on ec2 you need ensure you use realtime kernel with 1000hz timer.

http://voxilla.com/2009/02/13/asterisk-amazon-ec2/

About density:

For m1.small max lines usualy 20-30

For c1.medium it is near 80-100(safe value 80)

For other - to be calculated.

NOTE: number of lines depend of every single instance( general load on physical server) and can vary ALOT.

P.S. amazon ec2 is very bad choice for voip, for it cost better get hetzner.de dedicated server or vps service which grant asterisk be working ok like http://lylix.net/,http://sysadminman.net/ or http://apbx.net

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  • Thanks for your answer. About density provided by you - is it CPU bound, network or IO bound ?
    – user154659
    Nov 17, 2013 at 8:32
  • hard to say. For sure not i/o. Most likly CPU,but on EC2 network perfomance depend of instance type/cpu
    – arheops
    Nov 17, 2013 at 16:08

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