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RE: [Xen-users] Very bad network performance between domU and dom0

To: "Klaus Schmidinger" <Klaus.Schmidinger@xxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Very bad network performance between domU and dom0
From: "JHJE (Jan Holst Jensen)" <jhje@xxxxxxxxxxxxxxx>
Date: Fri, 26 Jan 2007 12:44:00 +0100
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Thread-topic: [Xen-users] Very bad network performance between domU and dom0
> JHJE (Jan Holst Jensen) wrote:
> >> I was able to obtain the xswindrivers.iso file that way and install
> >> it into my virtual Windows XP machine. Unfortunately, when 
> trying to
> >> reboot Windows immediately complained that it could not read from
> >> the hard disk, even though I did change the 'vif' and 'disk' config
> >> lines to
> >>
> >> vif = [ 'mac=00:16:3e:00:00:66, bridge=xenbr0' ]
> >> disk = [ 'file:/Data/xen/bat-xp.img,hda,w' ]
> > 
> > I think the PV drivers are SCSI-only, so I guess your disk 
> must be "sda"
> > instead. If you started out by installing Windows on a 
> virtual IDE drive
> > you may be hosed :-/.
> So I guess this means I should have installed Windows XP in a virtual
> SCSI drive. Ok, I changed my 'disk' line to
> disk = [ 'file:/Data/xen/bat-xp-scsi.img,ioemu:sda,w', 
> 'file:/Data/iso/windows-xp.iso,hdc:cdrom,r' ]
> and started the virtual machine on an empty bat-xp-scsi.img file.
> The Windows setup comes up, but complains that there is no hard
> disk installed in my computer.
> Is there anything else I need to configure to have Windows see
> an SCSI drive?

Hmmm.... This is interesting. The XenExpress help says:

"The current version of XenServer supports no more than 3 virtual disks
(Disk0-Disk2) for unmodified Windows Xen Virtual Machines. The virtual
disks appear to the Windows XenVM as SCSI devices if the paravirualized
drivers have been installed, or as IDE devices if the paravirualized
drivers have not been installed."

and when I look in the Xen config for my Windows VM, the LVM partition
is exported as "hda", yet when Windows is booted (with PV drivers) it
reports that the C: drive is a Xen PV SCSI drive. Fascinating. I did not
look at what Windows thought the hardware was before installing the PV

Can you boot the VM that you installed the PV drivers into if you change
the disk spec to be

  disk = [ 'file:/Data/xen/bat-xp-scsi.img,sda,w', ...

? I removed "ioemu", since the PV driver will bypass the ioemu layer -
as far as I understand it. Sorry that I can't be more specific, but I
have only started using HVM this week so I am learning as well :-).

-- Jan

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