Re: [Xen-users] streaming server on a virtual machine.

[Grant McWilliams <grantmasterflash@xxxxxxxxx>]

On Sat, Sep 26, 2009 at 11:28 AM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:

On Sun, Sep 27, 2009 at 12:56 AM, Mauro <mrsanna1@xxxxxxxxx> wrote:
> 2009/9/26 Grant McWilliams <grantmasterflash@xxxxxxxxx>:
>>
>> I will also add that if Xen has a bottleneck it's traffic between DomUs.
>> Don't configure it in any way to have
>> one DomU servicing another DomU unless both have real network cards
>> attached to them.

> Thank you for your answer it was very exhaustive.
> I've learned a new thing, that is the poor performance in traffic
> between domU in the same machine rather than domU in different
> machines.
> I've a domU with tomcat and many jruby applications and, in the same
> machine, another domU as database server with postgres.
> Based on what you say I've to reconfigure my systems to have domU in
> different machines.

Were you having network performance problems?
There was a thread on this list some time ago about domU <-> domU
network performance, and the ones that experience it were using newer
pv_ops kernels while people who use 2.6.18 kernel (like RHEL/Centos5)
or Suse -xen kernel got good performance.

http://www.nabble.com/Fw%3A-Re%3A-bridge-throughput-problem-tt25328188.html#a25351569

Instead of having a second physical server just to get decent
performance, I'd say it's easier to simply change your dom0 kernel.

--
Fajar

The domU to domU performance problem that I extensively tested and documented was with the 2.6.18 without pv_ops.
The problem does not appear if the traffic is routed straight out of the box. I saw full GB speeds from a DomU to any other machine.

I'd get about 350-400 Mb/s between DomUs. After changing every variable and digging through the xen-users and xen-devel archives
the answer I got was yes, that does exist and the solution was to assign a NIC to the domU or only have DomUs communicate with DomUs on

other physical machines. This was with Xen 3.2.1. I haven't rerun my testing with 3.4 yet because I worked around it.


Grant McWilliams



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