We started off asking a Digium representative about putting 4 quad-span cards in a single machine and got the following response:
- I'd use two machines, with two quad cards each. And then, I'd need to be using only the G.711 ulaw protocol. Then, I'd still use a mid-range dual Xeon CPU machine in the 2.4GHz+ spectrum.
David Mandelstam of the Asterisk Biz List provided me with this explanation:
- Zaptel drivers produce at least one interrupt per millisecond per board, which is minimal if the interrupt handlers are short. But on a heavily loaded machine doing lots of echo cancellation, each interrupt can approach 1 millisecond in length. So if there are interrupts coming from several cards, you can see how you could get into trouble.
So it looks like processor interrupts are the culprit.
Possible solutions to this problem include (please feel free to add to this list):
- An Asterisk slave server pool ( http://home.comcast.net/~mroth01/LargeAsteriskSetup.gif )
- A TDM-VoIP gateway (Cisco, Quintum, AudioCodes, Lucent)
- Using Sangoma cards (As per David Mandelstam, Sangoma cards use proprietary drivers and there are operational setups using 4 quads per machine)
I'm not confident that the Asterisk software scales well under certain conditions, such as using Monitor to digitally record 16 spans of voice channels, so solving the card issue may not be the last step in a large installation. If anyone has any insight on this, please post it to the list.
Hope that was helpful,
Matthew Roth http://www.voip-info.org/tiki-index.php?page=Running%20Asterisk%20on%20Debian
Matthew Boehm wrote:
From what I understand (and this could be completely wrong), the Digiumcards use a bunch of processor interrupts and too many cards will use up all the interrupts. (again, that could be completely wrong).
What kind of calls are they? G711->PRI? Not much CPU needed there. G729 -> PRI? Yes, you would need something along the lines of a dual Xenon 3.6Ghz do do that. Its all in the transcoding. If just passthru, not much cpu is needed.
-Matthew
_______________________________________________ Asterisk-Users mailing list [email protected] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
