Others have talked about the z/VM v. VMware question, but when Virtual Server
came up it made me think about how it sits against VMware.  As such it's
flagged OT, so read on at your peril.  :)

On Fri, Dec 10, 2004 at 11:17:04AM -0700, Ledbetter, Scott E wrote:
> They have been elusive about supporting Linux guests
> on their Virtual Server product. VMWare lists Windows, Linux, FreeBSD, x86
> Solaris and NetWare as supported guests.

Microsoft's Virtual Server product started life as Connectix Virtual PC, which
before it was ported to Windows was actually a PC virtualisation package for
the Mac (Microsoft acquired Connectix a couple of years ago).  In order to do
this they had to *completely* virtualise the PC architecture, since it was
a different architecture to that on which Virtual PC actually ran (680x0 or
PowerPC).

VMware, on the other hand, has only ever supported host and guest as the same
architecture.  They put some 'streamlining' in to pass some guest operating
system calls through to the host OS, in order to lessen the virtualisation
overhead.  That's why you can only run "mainstream" OSes as guests under
VMware[1].

Why does this matter?  Because Virtual PC (at least on the Mac, and I really
doubt the PC version was from a different code base) was a 'purer'
virtualisation environment.  I don't think there was *any* PC OS that you
could not run under Virtual PC: OS/2, BeOS, Linux, various DOS flavours, and
probably many more.  The fact that it was able to run with mostly comparable
performance to VMware Workstation on the same host was a credit to the
Connectix folk.

Now, that code base belongs to Microsoft.  Sigh.  Scott has alluded to the
direction Microsoft is taking what was Virtual PC -- but I'm over it, really
I am. :)

> I don't think there is an easy answer to your VMWare vs. z/VM question, and
> MS Virtual Server adds in a third possibility.  You would have to benchmark
> your specific apps and do your own cost study to get the correct answer for
> your environment.

If the guests are going to be Windows, MsVS is a definite contender.  How
Microsoft will address some of the very advanced features of VMware ESX will
be quite interesting, but you can bet that they will ensure that Windows runs
better under MsVS than it does on ESX. ;)

If the workload is Linux, then you'd have to be very wary about MsVS
(IMNSHO).  What might work today would definitely be unsupported by Ms, and
may become disfunctional in the future if (when?) Microsoft decides to make
MsVS a Windows-only virtualiser.

Cheers,
Vic Cross
<at home, speaking only for myself>

[1] VMware did a pilot of a version for Linux and Windows (before GSX and ESX
existed) that was enabled to run OS/2 as a guest, and it worked great -- but
they pulled the pin due to "lack of demand".  Did they really have to do that
much work to the code that a large demand was needed in order to maintain it?
Heh, maybe I was the only one that responded... :)

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