Re: [Xen-users] Speed of Xen Network Bridge Interface (10/100/1000?)

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I would like to learn the speed of the network bridge interfaces created by
> XEN.
>
> More specifically, on xenbr0, given that the traffic only occurs between my
> Dom0 host and PV DomU guest, am I limited to 10 Mbps, 100 Mbps or 1000
> Mbps? Does it depend on something such as ethernet card capability (even
> though the packets don't go out of the card and stay inside Dom0)?

It's not limited by your physical ethernet card, nor is it restricted to any 
particular maximum.  It's basically limited by how fast the Xen virtual 
network drivers and the Linux bridging code can move the data around.  This 
used to actually be slower a domU accessing the physical ethernet due to the 
extra memory operations that were required (and used a fair bit of CPU).  I 
think there have been some changes to reduce the bottleneck and improve 
intrahost performance since then, so it would be faster than I remember it.  
I'm not sure if it's currently faster than GigE; possibly.

It ought to be significantly faster than 100Mbps on a modern machine.  It'll 
act like a really fast ethernet card, with no hard limit on the transmission 
speed (instead, transmission speed will be limited by how powerful your 
machine is and how efficient the virtual ethernet code is).

> I plan to use iScsi or Ata-over-Ethernet, that's why I'm asking this
> question,

Is that from dom0 to domU?  Do you have a particular reason for doing that?  
Using blkback / blkfront would be simpler and more efficient.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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