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RE: [Xen-users] Disk IO trouble in Xen

  • To: "Greg Hellings" <greg.hellings@xxxxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "Ross S. W. Walker" <rwalker@xxxxxxxxxxxxx>
  • Date: Tue, 6 May 2008 13:18:20 -0400
  • Delivery-date: Tue, 06 May 2008 10:18:51 -0700
  • Importance: normal
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Priority: normal
  • Thread-index: Aciu+W7brUb+EBrsEd2umQAX8t0tvQAAWDiwACcvwbEAAVB7gA==
  • Thread-topic: [Xen-users] Disk IO trouble in Xen

Greg Hellings wrote:
> So I tracked down my network freezing issues.  I have a few xen servers all
> connected to the same network I'm working with here. All of them I used the
> virt-manager tool to install.  One of the other hypervisors had a domu
> running on it that virt-manager had chosen the same mac address as the domu
> on the hypervisor I was having problems with.

Good news. It's always the last place you look...

> I still see the same performance difference between the dom0 and domu when
> using hdparm -tT, but maybe that isn't a good test.  I do notice that if I
> run hdparm over and over on the domu's the numbers improve, suggesting that
> caching is effecting the out come.  Under iozone, the number between domu
> and the dom0 are almost exactly the same.

Well when doing aio through the VFS layer to an image file you will loose
some performance. It is the sacrifice you make in order to gain flexibility.

Everything's a trade-off.


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