Xen users - Sep 2008 - Using xen in multihead distributed setup

I''m new to xen and hope that this question is not too daft but I just
need a
short answer. Can I run say four servers within xen on one box with 4 video
cards, where each server is tied to one of the video cards, so I have a view
of applications running on the various servers concurrently.

John


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On Thu, Sep 25, 2008 at 2:46 PM, John Preston <byhisdeeds@gmail.com>
wrote:
> I''m new to xen and hope that this question is not too daft but I
just need a
> short answer. Can I run say four servers within xen on one box with 4 video
> cards, where each server is tied to one of the video cards, so I have a
view
> of applications running on the various servers concurrently.
>
> John
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>
PCI Passthru does not work with video cards, instead you can access
the video display from the vm''s using vnc or sdl.

Andy

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>
> PCI Passthru does not work with video cards, instead you can access
> the video display from the vm''s using vnc or sdl.
I don''t think I can use vnc or sdl in my case. I need each server to
run X
which I thought would be able to distinguish between all the installed cards
by their n:n designation in xorg.conf. I was hoping that there would be a
way to bind each servers X output to just one video card. Thus I could see
the output of applications  running on each server.

John


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John Preston wrote:
> 
> 	PCI Passthru does not work with video cards, instead you can access
> 	the video display from the vm''s using vnc or sdl.
> 
> I don''t think I can use vnc or sdl in my case. I need each 
> server to run X which I thought would be able to distinguish 
> between all the installed cards by their n:n designation in 
> xorg.conf. I was hoping that there would be a way to bind 
> each servers X output to just one video card. Thus I could 
> see the output of applications  running on each server.
You can use X in dom0 as a server for the domUs.

Just setup X servers with XDMCP in dom0 on the virtual consoles
of your choice. You can have them pinned down to certain domUs
or have the XDMCP client broadcast/multicast for the active
domUs to service.

You could even have particular domUs bring up SDL on a particular
X display in recent Xen implementations through a config option
(is it display?).

-Ross

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>
> You can use X in dom0 as a server for the domUs.
>
> Just setup X servers with XDMCP in dom0 on the virtual consoles
> of your choice. You can have them pinned down to certain domUs
> or have the XDMCP client broadcast/multicast for the active
> domUs to service.
>
> You could even have particular domUs bring up SDL on a particular
> X display in recent Xen implementations through a config option
> (is it display?).
> I''m trying to implement a cheap wall display. So using some
example
> numbers, a box with 4 video cards and 4 instances of linux running within
> xen, with each being bound to a particular card. Then I have another
machine
> or instance which uses XDMX an X proxy, which manages the 4 displays as
one.
>
> So it sounds like I can run my individual X instances all under xen instead
> of having to buy individual boxes. Right?
>
> John

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On Thu, Sep 25, 2008 at 11:49 AM, John Preston <byhisdeeds@gmail.com>
wrote:
>> I''m trying to implement a cheap wall display. So using some
example
>> numbers, a box with 4 video cards and 4 instances of linux running
within
>> xen, with each being bound to a particular card. Then I have another
machine
>> or instance which uses XDMX an X proxy, which manages the 4 displays as
one.
you don''t need Xen at all for this.  you could run 4 X processes on
the same machine, each using one display.

or maybe there''s a multidisplay driver for X.org?

-- 
Javier

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>
> you don''t need Xen at all for this.  you could run 4 X processes
on
> the same machine, each using one display.
> or maybe there''s a multidisplay driver for X.org?
Forgive my ignorance as I''m not too up on the X server implementation
details, but wouldn''t there be a conflict when I''m sending
messages via the
network to each of the servers as they all use the same tcp port on the one
machine?



John


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On Thu, Sep 25, 2008 at 12:23 PM, John Preston <byhisdeeds@gmail.com>
wrote:
>> you don''t need Xen at all for this.  you could run 4 X
processes on
>> the same machine, each using one display.
>>
>> or maybe there''s a multidisplay driver for X.org?
>
> Forgive my ignorance as I''m not too up on the X server
implementation
> details, but wouldn''t there be a conflict when I''m
sending messages via the
> network to each of the servers as they all use the same tcp port on the one
> machine?
you can specify the port for each one


-- 
Javier

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John Preston wrote:
> 
> 	You can use X in dom0 as a server for the domUs.
> 	
> 	Just setup X servers with XDMCP in dom0 on the virtual consoles
> 	of your choice. You can have them pinned down to certain domUs
> 	or have the XDMCP client broadcast/multicast for the active
> 	domUs to service.
> 	
> 	You could even have particular domUs bring up SDL on a particular
> 	X display in recent Xen implementations through a config option
> 	(is it display?).
> 
> I''m trying to implement a cheap wall display. So using 
> some example numbers, a box with 4 video cards and 4 
> instances of linux running within xen, with each being bound 
> to a particular card. Then I have another machine or instance 
> which uses XDMX an X proxy, which manages the 4 displays as one.
> 	
> So it sounds like I can run my individual X instances 
> all under xen instead of having to buy individual boxes. Right?
Well, I''m a little lost on what your trying to accomplish. The
current Xorg implementation in CentOS 5 supports multi-head
displays in a wall configuration out-of-the-box, though for
multiple adapters to work effectively they should be the
same model. I suggest 2 dual-head adapters of the same
type, say PCIe and a host system with 2 PCIe slots of the
same speed. Any more then 2 and you will start running into
problems finding machines that have the number/type of slots
available, not to mention IRQ overlapping, bus contention,
and driver instability.

Wikipedia is always a good place to start. Then I would
look at the Xorg docs on your system, you might be
surprised at some of the advanced configurations it''s
capable of.

-Ross

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John Preston wrote:
> I''m new to xen and hope that this question is not too daft but I
just
> need a short answer. Can I run say four servers within xen on one box
> with 4 video cards, where each server is tied to one of the video
> cards, so I have a view of applications running on the various servers
> concurrently.
>
There is one of the CoolConfigurations on the Xen wiki that does
something similar to this.

http://wiki.xensource.com/xenwiki/CoolConfigurations?highlight=(cool)#head-f4e3242c0008f33dfe01a8467a011efad1723ad2

I haven''t tried this but sounds like with enough hacking one can get it
to work. Although the author of the configuration wasn''t very specific,
I am guessing he did PCI pass thru to a paravirtualized domain. It wont
work with Windows or a fully virtualized guest. But with some patience,
it might work. Again, I haven''t tried this solution so it might be
smoke
and mirrors.

Mike

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