Re: Xen vs VMware

[Bill Hacker <wbh@xxxxxxxxxxxxx>]

Steve Mynott wrote:
> On 10/18/06, Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> >     Generally speaking I prefer the VMWare concept over the Xen concept.
> >     Xen actually has to run two operating systems, one serving as the
> >     master and the other as the 'guest' OS, and this compounds the
> >     number of potential bugs you might run into a lot more then a machine
> >     emulator does.
>
>
> I'm surprised by this.  Xen (abstracting out some sort of meta
> operating system) seems a "cleaner" and simplier solution to me than
> running a  complex software copy of real hardware.
>
> Anyway aren't we just talking about lines of C in both cases?  I
> suspect the number of bugs in either would just be a function of the
> total lines of C.
>
> Xen is relatively small.   Although vmware source, isn't available
> AFAIK would anyone care to estimate lines of source for it?

Given that it is a commercial product?

Aren't such coders paid by printout-weight?

;-)

More seriously - look at the sizes of the binaries. The compiler has (hopefuly) 
sweated the worst of the diffrences out by then, else it would be far slower 
than it is..)

VmWare not only has to emulate an entire machine, it has to also 'virtualize' 
the peripheral I/O & fs - and therein lies a bit of a mystery.

I've had my hands on a lot of these sort of products over the years, and one of 
the more curious experiences came out of the Connectix/InnoTek (Now Microsoft) 
'Virtual PC' - from Intel/AMD O- used on OS/2 & Windows thru OSX G4 versions.

Whether 'benchmarks' or day to day, experience will vary all over the lot, but 
over time the curiosity was that a 'typical' VPC-emulating-Intel on-Intel with 
FAT fs seemed to run about 40 to 50% of the speed of the underlying hardware.

Actually quite decent if one had a 1 or 2 GHz platform and had become accustomed 
to a 400-500 Mhz one anyway.

The curiosity was that VPC-emulating-intel on-PPC-G4 wiht hfs(+) was much faster!

Approximately 700 MHz Intel performance on a mere 1 GHz G4. And I don't kid 
myself that OSX is anywhere near as efficient as OS/2 (or necessarily even a 
'stripped for combat' industrialized-version of NT - see LitePC).

So - some of these are well-debugged and refined products.

Matt's viewpoint and mine do differ, though.

I'd like to see a 'DragonXen' to use for 'mothership' of baby Dragons, and 
Beasties in general.

Something more akin to big-iron VM/MV - 'in between' having to emulate 
*everything* and bare-bones 'meet me half way or go panic yerself' Xen.

AIX-5L-like, perhaps..?

If/as/when I am ever moved to an Intel-ized Mac (d'ruther have polio..), 
'Parallels' is on my 'must try' list.

But to run *BSD guests and legacy OS/2, not WinWoes!

What with dualcore and more we are on the brink of a whole new set of major changes.

83 year old mum just told me of a schoolmate of hers, gone deaf, who is now 
reliant on a real-time speaker-independent speech-to-text telephone with screen.

Yesterday's lab gear is today's appliance....

Bill









Bill