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

[Stephan Seitz <s.seitz@xxxxxxxxxxxx>]

Hi!

Just to add some salt to the original posters question, I'm going to migrate
clustermembers into domU's on one big machine.
Well, it's not a full featered HA cluster, it consists of one huge nfs/nis
server and a lot of diskless servers with as little as necessary failover
management.
First tests showed, that booting one of the machines as domU results in
random disk throughput of about 10 MB/s against about 80-95MB/s when running
on bare-matel.
I don't necessarilly need to keep the current infrastructure, but I'll 
definitely
need one mountpoint available on many (expandable) machines.
Is there some best-practice description on how to get one mountpoint available 
to
a lot of domU's ?

Thanks for any suggestion!

Stephan



Mark Williamson schrieb:
>> 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
> 


-- 
Stephan Seitz
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