Martin,
This is a shot in the dark, but, this seems to be a IO scheduling
issue.
Since, i am late on this thread, what is the characteristic of
the IO: read mostly, appending writes, read, modify write,
sequentiality, random, single large file, multiple files.
And have you tracked whether any IO is aged much beyond 30
seconds if we are talking about writes.
If we were talking about Xen by itself, I am sure their is
some type of schedular involvement, that COULD slow down your
IO due to fairness or some specified weight against other
processes/ threads / tasks.
Can you boost the scheduling of the IO task, by making it
realtime or giving it a niceness or .. in a experimental
environment and comparing stats.
Whether this is the bottleneck of your problem would take
a closer examination of the various metrics of the system.
Mitchell Erblich
-----------------
Martin wrote:
>
> > The behaviour of ZFS might vary between invocations, but I don't think that
> > is related to xVM. Can you get the results to vary when just booting under
> > "bare metal"?
>
> It's pretty consistently displays the behaviors of good IO (approx 60Mb/s -
> 80Mb/s) for about 10-20 seconds, then always drops to approx 2.5 Mb/s for
> virtually all of the rest of the output. It always displays this when running
> under xVM/Xen with Dom0, and never on bare metal when xVM/Xen isn't booted.
>
>
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