Capacity Planning for Asterisk PBX



  • Something I've noticed and not sure it's been discussed before is this :-

    On their site the "Community Edition" supports *Unlimited Simultaneous Calls
    looking down a bit we see for the * *Limited by the server's capacity.

    How do you size a PBX box? vCPU/RAM/Disk



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    Something I've noticed and not sure it's been discussed before is this :-

    On their site the "Community Edition" supports *Unlimited Simultaneous Calls
    looking down a bit we see for the * *Limited by the server's capacity.

    How do you size a PBX box? vCPU/RAM/Disk

    I believe you mean VitalPBX? Or are you asking about Asterisk in general?

    And the answer is, as always, it depends.

    If you are not doing any transcoding of audio formats, then 1 CPU and 1GB or ram will do thousands of idle extensions and likely 10's to 100+ simultaneous calls.



  • Yeah it was more a "General" PBX question with what ever favour you want VitalPBX, Asterisk, FreePBX.

    So for us if we wanted a unified system company wide we would need to host (On-prem in a VM or Cloud) a machine that would be capable of having
    300+ Phones/Extensions.
    40 simultaneous calls.
    Voice mail for may 30% of the phones/extensions.

    I say Phones/Extensions, as for us in IT we would most probably use our PC's as the phones and use mobiles when out on sites.



  • @JaredBusch said in Capacity Planning for Asterisk PBX:

    If you are not doing any transcoding of audio formats,

    If we are doing Transcoding how would that effect the specs, I guess you would need more as there is more "processing" of the call audio?



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    Yeah it was more a "General" PBX question with what ever favour you want VitalPBX, Asterisk, FreePBX.

    So for us if we wanted a unified system company wide we would need to host (On-prem in a VM or Cloud) a machine that would be capable of having
    300+ Phones/Extensions.
    40 simultaneous calls.
    Voice mail for may 30% of the phones/extensions.

    I say Phones/Extensions, as for us in IT we would most probably use our PC's as the phones and use mobiles when out on sites.

    a standard $5 Vultr instance can handle this.
    1vCPU
    1GB RAM



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    @JaredBusch said in Capacity Planning for Asterisk PBX:

    If you are not doing any transcoding of audio formats,

    If we are doing Transcoding how would that effect the specs, I guess you would need more as there is more "processing" of the call audio?

    Correct. And it again depends. Transcoding ULAW/ALAW to OPUS it light. Going to G.729 on the other hand costs a lot of CPU.



  • @JaredBusch said in Capacity Planning for Asterisk PBX:

    a standard $5 Vultr instance can handle this.
    1vCPU
    1GB RAM

    And this is why I ask the question 🙂 as I would of thrown (if on prem) 2-4 vCPU and 4-8GB RAM 😃
    But that's only from what I've seen and been told (OK By sales reps).

    We were asked to spin up a Linux VM 4vCPU 6GB RAM 500GB HD to handle this sort of system.



  • @hobbit666 you can always start small and upscale if you need more. Going from a higher capacity system to a lower capacity one is where issues often arise.

    So starting at 1:1 is a decent place to start for a lot of systems.



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    How do you size a PBX box? vCPU/RAM/Disk

    For us, we are almost always forced to built boxes so much larger than needed that it rarely comes up. In our experience, running into transcoding needs is rare these days (used to be common) so CPU needs generally remain really low. And even 512MB is enough to run as many calls as we typically see. But we don't deploy anything smaller than 1GB in production because of what is offered from cloud providers. Because of that, we always have an excess of RAM.

    On the rare occasion that we are needing more capacity, it is normally for disk space, not CPU or RAM. And with CPUs getting faster every year, and calls not changing, a modern single vCPU machine can handle so many more tasks than one years ago. And something like VitalPBX needs much less CPU to run the interface than something like FreePBX does, so we are seeing the CPU needs staying flat or decreasing, while seeing the minimum available CPU increasing.

    Even a pretty mammoth deployment you'd unlikely want more than 2 vCPU and 2GB RAM.



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    Yeah it was more a "General" PBX question with what ever favour you want VitalPBX, Asterisk, FreePBX.

    So for us if we wanted a unified system company wide we would need to host (On-prem in a VM or Cloud) a machine that would be capable of having
    300+ Phones/Extensions.
    40 simultaneous calls.
    Voice mail for may 30% of the phones/extensions.

    I say Phones/Extensions, as for us in IT we would most probably use our PC's as the phones and use mobiles when out on sites.

    I would say that that is well below the "planning" threshold and isn't enough to warrant looking at anything above the "minimum" options.



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    @JaredBusch said in Capacity Planning for Asterisk PBX:

    If you are not doing any transcoding of audio formats,

    If we are doing Transcoding how would that effect the specs, I guess you would need more as there is more "processing" of the call audio?

    It uses CPU, a lot of it.



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    @JaredBusch said in Capacity Planning for Asterisk PBX:

    a standard $5 Vultr instance can handle this.
    1vCPU
    1GB RAM

    And this is why I ask the question 🙂 as I would of thrown (if on prem) 2-4 vCPU and 4-8GB RAM 😃
    But that's only from what I've seen and been told (OK By sales reps).

    We were asked to spin up a Linux VM 4vCPU 6GB RAM 500GB HD to handle this sort of system.

    Fire those reps right now! Bring in some experts. If the phone company doesn't know anything about their own phones, how well could they possible support it?



  • @scottalanmiller said in Capacity Planning for Asterisk PBX:

    Fire those reps right now! Bring in some experts. If the phone company doesn't know anything about their own phones, how well could they possible support it?

    We did 😃



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    @scottalanmiller said in Capacity Planning for Asterisk PBX:

    Fire those reps right now! Bring in some experts. If the phone company doesn't know anything about their own phones, how well could they possible support it?

    We did 😃

    I know a guy that it used to dealing with GMT+9 (so GMT+7 should be solid) call times if you need 😛



  • @hobbit666 said in Capacity Planning for Asterisk PBX:

    @scottalanmiller said in Capacity Planning for Asterisk PBX:

    Fire those reps right now! Bring in some experts. If the phone company doesn't know anything about their own phones, how well could they possible support it?

    We did 😃

    Good deal!



  • It really depends. If you don't do software transcoding even hundreds of call on quite low power hardware would be fine (say 2GB ram and 4 CPU cores).

    We've found that using a Sangoma E1 card the same hardware would handle the double of the calls, only because Asterisk bases its timing source on the Sangoma hardware instead of using the dummy one.

    One test that you can do is to run the command dahdi_test, the values should be not less than 99.996% for a good audio quality, specially for music on hold and conference rooms.

    There are some hardware timers that do the same job for a very low price, ie

    https://www.thedebugstore.com/asterisk-pbx-system-timer-cards/


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