Re: [Xen-users] Is Xen a way to go for me?

[Paul Schulze <avlex@xxxxxxx>]

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Hi,

On 6 May 2009, at 17:02, Torben Schou Jensen wrote:

> Hi
> My current desktop at home is a DELL DIMENSION 8100, got it in 2001,  
> still
> a good machine but makes little to much noise and sometimes a little  
> slow
> due to only 768MB ram.
> It's setup for dual boot with WinXP and Debian.
> http://swampthing.dk/~tsj/hardware/#nDELL_DIMENSION_8100
Thats still a good machine, in fact, if you can live with the fact  
that you can't run Windows as a DomU (needs IVT/AMDV for HVM mode),  
you can at least use it to test what Xen can do for you. That would be  
very important, because Xen is heavily geared towards server  
application and might miss some features, you know from other  
virtualization solutions for workstations and desktop (Qemu,Virtual  
Box, VMware Workstation and so on). If you want to try running  
Windows, just use Qemu, that should give you a pretty good idea on how  
it would run in Xen HVM mode (although it might be slower, because  
your CPU is missing IVT).
> So for some time I have been thinking of a change to new hardware,
> and it would be great by Virtualisation to have WinXP and Debian  
> running
> at same time.
>
> I currently have a good look on a barebone like Shuttle XPC SG31G5,
> a lot of ram and a VT enabled Intel processor.
You don't need too much RAM, in your case, 4GB should be the maximum.  
I also don't think that the Shuffle barebone is a good choice, because  
you will be restricted concerning CPU/Mainboard upgrades (and  
subsequently feature upgrades), which can be very important for what  
you want to do. A normal PC case or an ATX size HTPC case would  
probably work much better here and give you a completely free hand in  
choosing your components for a maximum of virtualization features like  
Intel VT-d or AMD IOMMU (and you will need those). You should check  
the mailing lists for success stories and take a close look at the  
specs before buying your hardware, because all the really interesting  
stuff for Desktop/Media application is still a little sketchy.
Also remember, even though the Shuffle seems to use a mobile CPU, the  
overhead from running Windows in HVM and Debian in Dom0 and DomU will  
increase the CPU temperature(depending on the HVM overhead mostly) and  
therefor raise the noise level (which might not be so nice for such a  
slim case).
If you want low power consumption, AMD is currently the way to go even  
if they are a little behind on speed. But you should wait about half a  
year, so they can get their new desktop chipsets (which will hopefully  
finally include IOMMU) and low power AM3 CPUs out.
> But now the point that keep me back.
>
> Only Dom0 have direct access to graphics card, so a way could be to  
> setup
> Debian with full X on Dom0 and use this to VPN / rdesktop into the
> different DomU, one with WinXP and one with Debian as I have now.
> As Internet traffic primary will be from DomU and out I see no risks  
> for
> Dom0, other than from time to time OS on Dom0 might need to download
> updates.
> Any bad things about using Xen this way???
>
> I know it will not be possible to use heavy graphics on a DomU  
> WinXP, but
> how about support for USB devices, soundcard etc???
> Will it be possible within DomU WinXP to enjoy a DVD movie including  
> sound???
Support for USB devices as well as sound support are available for HVM  
DomUs, but with limitations. Almost all the USB devices, I have ever  
tested with any virtualization technology (VMware, Qemu, VirtualBox,  
Parallels and Xen) seem to have problems with performing certain  
operations like Firmware upgrades. Besides that, you should expect to  
have to attach and detach USB devices to DomU manually at least the  
first time, you connect them (maybe every time, didn't play with it  
too much).
The Qemu sound drivers (especially es1370) seem to be pretty advanced  
by now, but since it is based on an older card, I doubt you will be  
able to get 5.1 sound out of it, to really enjoy DVDs. If you really  
need 5.1 surround sound, you will probably have to either run it  
through a sound server in Dom0, or pass the sound card through to the  
Windows DomU (VT-d/IOMMU needed).
Also note, that at least in PV mode (usually used for Linux), it does  
not yet seem to be possible to use a CD/DVD effectively inside a DomU  
without passing the  IDE/SATA/SCSI controller through. PvSCSI could do  
much for this problem, but as of version 3.3.1, it still does not seem  
to work properly with SATA drives (and probably IDE) of linux. You  
should also expect problems with burning CDs/DVDs from the Windows  
DomU (you'll probably have to do that in Dom0).
On the bright side though, with the right hardware and a VT-d or IOMMU- 
enabled mainboard chances are, that you could succeed in passing your  
graphics card to the Windows or Linux DomU, which as far as I know  
isn't possible in other virtualization solutions and would ultimately  
improve performance, including DVD playback, since most graphics cards  
ship at least with basic decoders and you get rid of the VNC middle man.
I hope, this isn't too confusing,


Paul.

- --
Paul Schulze
Mail: avlex82@xxxxxxxxx

Why can't a programmer tell the difference between Halloween and  
Christmas?
Because OCT31 = DEC25.

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