Re: [Xen-users] XEN hangs on IO operations?

[Steven Timm <timm@xxxxxxxx>]

On Wed, 5 Mar 2008, cold80 wrote:

> We bought a dedicated server with CentOS 5.1 and XEN (3.x). I've installed
> Win2003 as the first guest but I noticed this simple (but terrible) problem.
> When I copy something quite big (like an iso image or something like that)
> on the host machine (from a directory to another for example) the VM hangs
> and I see CPU usage going to 0. The VM hangs for about 5 minutes, then
> magically it wakes up and continue working well. During these 5 minutes the
> VM doesn't respond to everything. The host, on the contrary, works without
> problems during the hang up. Do you know what can it be?
>
> Thanks a lot
>
> Cold
There are various kinds of I/O on the host dom0 that can cause
the xen domains to block because the network interrupts of the domU are 
not getting serviced properly by the dom0. I have seen errors very much 
like that and have only resolved them by shifting all the processes
off of the dom0 to other xen instances.  The signature of this is
if you have a continuous outbound ping going on a domU during this
time, it will give you no output during the hang and then all of
a sudden all the ping packets will report back at once once the hang is 
done.
Steve


--
------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
timm@xxxxxxxx  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.

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