Re: [Xen-users] vif interfaces drop packets

["John Madden" <jmadden@xxxxxxxxxxx>]

> So this is really a traffic
> shaping routine (very very basic); it would be better e.g. to delay tcp
> packets if the buffer gets crowded since tcp stacks would react on the
> delay and adjust their sending speed; but this is not possible because the
> host machine does not "see" tcp traffic but only bridges the frames. This
> leads to another problem: if your guests are in a network with high
> broadcast load the buffers get filled with theses broadcasts too.
> So after all, IMHO it's a general design problem of virtual machines which
> have to emulate the interrupts of real hardware.

In other words, routing rather than bridging may be advisable?  Routers at least
have queues and are designed to handle these sorts of situations, right?  At the
very least, Linux QoS principles could be applied on dom0 to prioritize packet
flow to the more critical domU's...

> PS: What type of applications do you run on the productive xen machines?
> What is your overall experience (beside the network issue ;-)) ?

We're running our internal FTP server, a web development machine, our enterprise
Helpdesk application, and eventually the nagios installation will actually be
doing something.  Feel free to quote me on it: Xen has changed the way I do my
job.  It's every bit as disruptive a technology as the SAN we installed earlier
this year.  It has been and will continue to be a key element in the 
consolidation
of hardware, simpliciation of infrastructure, and ease of management.  It's
quickly becoming one of those "how did I live without this software" pieces of
software.  ...And I'll happily go on all day about it. :)

That said, customers don't like packet loss and it doesn't matter how good Xen 
is
if  their ssh sessions hang every few minutes.

John





-- 
John Madden
UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@xxxxxxxxxxx


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