[OpenSIPS-Users] [MediaProxy] desirable media-relay server attributes

[Dan Pascu]

On 3 Jan 2011, at 22:41, Jeff Pyle wrote:

> Hello,
> 
> I'm spec'ing out some servers to be media relays running Mediaproxy 2.4.x.  Assuming a standard Debian stable install with the appropriate packages pulled from testing, which attributes are most desirable:  fewer, faster processing cores or more, slower processing cores?

I do not think the CPU will be limiting you. Consider that Cisco routers do not have multiple cores, yet still manage to route traffic that saturates their interfaces.

The most limiting factor will be your network card. RTP traffic consists in a lot of small UDP packets (even as low as a few bytes). That means that the network card will have to deal with a lot of packets and most standard cards generate one interrupt per packet received. As a result your CPU will be saturated with handling interrupts, not with the actual processing/forwarding of the data.

Probably more cores can help here given that they handle interrupts independently, so the more core you have the more interrupts you can handle. But that is only true if the interrupt handling is independent per core and not shared by all cores.

The best you can do is get some smart network cards that can aggregate multiple packets received and only send 1 interrupt for a bunch of them, thus relaxing its burden on the system.

> 
> For example, would it be better to have an 2 processor box each with 8 cores at 2.0 GHz (AMD), or a box with 2 processors each with 4 cores at 3.6 GHz (Intel)?  I'm not interested in the brand warfare but rather the question of speed and quantity of processing cores.
> 
> I would imagine this comes down the multithreaded ability of the linux kernel and how the conntracks use it.  There are those on this list with much more knowledge and experience than I at these things.  Any thoughts?
> 
> Also, would memory speed come into play here, or would I run out of bandwidth way before it would matter?

I don't think memory bandwidth will be an issue. Mediaproxy only makes your linux box act as a dedicated router with specific routing rules. Linux is perfectly capable of working like that, people use it as a router and drive up to 34GBps/s with a box. As I said your biggest problem will be given by the insane amount of small packets the system needs to process that generate too many interrupts from most network cards. 

--
Dan