13 Jun
2009
13 Jun
'09
5:16 a.m.
2009/6/12 Sridhar Ayengar <ploopster at gmail.com>:
Eric Smith wrote:
That's incredibly shortsighted of them to ignore such a powerful feature.
Traditionally, that was the way that operating systems would be developed
and tested for compatibility with newer machines at IBM. ?The hardware
wouldn't be ready yet, so the OS people wouldn't have a machine to use for
their development work. ?It's a chicken-and-egg problem. ?It was solved by
developing a version of VM that emulates the new machine, and running it as
a guest under VM on an *older* machine.
My guess would be that this is a little protective colouring of the truth.
A VMware guest only delivers about 80% of the performance of the raw
hardware, because all the kernel code - all the core OS itself, all
device drivers etc. - are running in a software emulator. And on a PC,
this is a lot more critical than on a mainframe, because PC software
is far more CPU (and graphics) intensive.
Run a VM under a VM, this would be even slower - you'd only get about
64% of the performance and my guess is that if it worked at all,
VMware feel it would make their product look bad.
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Well, there is one feature that VM has that I've not seen in many other
situations. ?VM can run as a guest under VM.
I asked engineers at VMware why their products won't do this, expecting
that it would be due to some limitation in their virtualization technology.
?I was dumbfounded when they explained that they deliberately prevent it in
order to avoid confusing their users. ?:-(
If that's the real reason, they should have a way for a sophisticated user
to set something in a .vmx file to enable it.