RE: [Xen-users] XEN and Windows Guests in critical environment(hospital)

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> Hi all,
> 
> One friend of mine are thinking about how to implement virtualization
in
> their critical job environment (a hospital).
> The main "problem" is there are a lot of medical application builded
in
> .NET tecnology; so, I view three possible options:
> 
> 1.  Win server with VMware and win guests (IIS to support .NET).
> 2.  UNIX/Linux server with XEN (or XenEnterprise) and win guests
> 3.  UNIX/Linux server with XEN (or XenEnterprise) and UNIX/Linux
guests
> (Apache with mod_mono to support .NET)
> 
> I think the next about each one option:
> 
> 1. The current preference because stability and windows compatibility.
> 2. My personal preference, but I'm not sure about the performance of
win
> guests on XEN Unix based system.
> 3. The "ideal" economical solution, but probably the more insecure in
> terms of stability.
> 
> Let me to repeat: it's a CRITICAL environment and will be not any
> error-edge.
> 
> Any argued reasoning will be welcomed.

In theory, all of the above options you mentioned add a layer of
complexity to the problem and therefore potentially reduce reliability.

I'm guessing, but there is a good chance that the critical applications
you speak of have been designed and tested in an un-virtualised
environment running on a Microsoft operating system. (I'd question
running critical applications in a Microsoft environment at all, but
that's another argument :)

By taking the applications out of the environment they have been
designed and tested in, you are almost certainly moving into an
environment that the company that designed the software can't or won't
support.

What if you have a problem? Who are you going to call? You need someone
that can drop everything they are doing and work on the problem. If you
are running VMWare+Windows+.NET or Xen+Windows+.NET, and an application
starts crashing, what do you do? The problem could be related to the
hardware, related to the virtualisation layer (VMWare/Xen), related to
windows, related to .NET, related to the actual application, or some
combination of all of them. Your support agent needs to be able to work
on the problem as a whole... I find it hard enough diagnosing obscure
problems when virtualisation isn't involved, and the last thing you want
is one of the vendors throwing their hands in the air and saying
'Xen/VMWare'??? We don't support that!!!

My argument therefore is that if these applications are as critical as
you say they are, give them exactly the environment they were designed
for, or at least get the approval of the software developers and testers
before you do anything. In fact I would have thought that critical
applications like this would be supplied essentially as a 'black box'
solution, and if anything goes wrong the supplier deals with it...

James


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