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Re: [Xen-users] Consolidating machines using xen

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Consolidating machines using xen
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Sun, 13 Jul 2008 19:39:44 +0100
Cc: James Pifer <jep@xxxxxxxxxxxxxxxx>
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On Sunday 13 July 2008, James Pifer wrote:
> I've been using xen at work for several months and pretty happy with it.
> I'm currently running several machines at home and I'm thinking about
> picking up some new hardware and consolidating them.
> The machines I have are:
> myth backend on FC9
> myth frontend on MythDora (FC8)
> mail/dns/dhcp/web server on FC5 (I know, old...)
> multi-purpose/storage machine (FC9)
> Windows XP machine - some windows utils, Nero burning, etc
> Some of these would need direct access to PCI cards. mythtv needs access
> to three tuner cards.

Well, that's generally doable under Xen as long as the PCI cards don't show 
any driver bugs when they're used in a VM!

> Not sure I would try the myth frontend machine. Could I have a domU have
> direct access to a specific video card? (nvidia fx5200)

Not easily, no.

> Windows XP would need direct access to DVD-RW drives. Or at least be
> able to use them as writers. Possible?

Not easily, no.  VirtualBox can do that, I think, although I don't know how 
solidly / generally it works (never tried it).  Not straightforward to do 
under Xen.

> Of course I have to get the "boss" to approve, but I'm thinking about
> this hardware:
> Motherboard:
> http://www.ecost.com/Detail/MOTHERNOARDS/GIGA-BYTE/GA-P35-S3G/40399167.aspx
> Processor:
> http://www.ecost.com/Detail/Processors/Intel/BX80562Q6600/34990428.aspx
> Then I would add a couple SATA hard drives and 4 gig of RAM (2x2048),
> allowing for an additional 4 gig later.
> Am I nuts or could this work?

Yes, could work.  Rather depends on what you're doing though / what you're 
trying to achieve.

Things to look out for:

If your myth backend is encoding 3 streams from TV tuners, it's surely going 
to be fairly CPU hungry?  You'll need to bear in mind that it needs *enough* 
CPU sufficiently *often* to encode without drop-outs.  This may affect the 
number of virtual machines that can share the box with it successfully, or at 
least it should inform the scheduler setup you do.

Giving graphics cards to domains other than dom0 is currently a bit hairy 
still.  The situation is improving (and hardware advances are helping) but I 
wouldn't suggest you necessarily do it unless you're willing to spend some 
extra time hacking at trying to make it work!  If you were using VT-d capable 
hardware you could, in theory, pass the primary graphics card to a HVM domU - 
possibly depending on the make of the graphics card (some have had issues 
working in this way).

Interacting with Windows over the SDL or VNC viewers is not especially snappy, 
so you may want to consider trying out the Open Source rdesktop tool...

For the storage machine - although this should work well under Xen (and you 
could either use a generic Linux distro or install something like OpenFiler 
or Zumastor on there to make it behave more like a "real" filer) -  another 
option would be to get a special purpose box like an NSLU2 (just an idea).

Good luck anyhow, hope you have fun whatever you do.


Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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