[OT] Virtualization (WAS: UNIX V7)

[Pontus Pihlgren]

On Fri, Jun 12, 2009 at 03:51:18PM +0100, Liam Proven wrote:
> > I'm curious, what OS:es and software did virtualisation before
> > VMware/XEN/Virtualbox and the like ?
> 
> Answered in detail by others, but I'd also point out some non-OS
> hypervisors that were around long before VMware etc. Sheep Shaver on
> BeOS in 1998, for instance.

Thanks everyone who shared information on this topic. I suspected there 
had been VM's done before, I was surprised by some of the incarnations.

> > And finaly, why would keeping virtual installations up to date be any
> > harder than non-virtual?
> 
<snip>
> great servers running all those as guests, you *still* have 50 copies
> of Windows to maintain. The work level doesn't drop much at all - you
> just save space and electricity.
</snip>

This was my point, the work level doesn't drop, but it certainly does 
not increase!

> And even that is a partly illusory saving, because much of the power
> and resources that a computer will use in its typical working life of
> a few years is spent in building the thing. So by replacing multiple
> working hardware boxes with a single big new machine to run the same
> workloads, you're wasting all that sunk-cost of the manufacture of
> those boxes, while "spending" a load more non-recoverable resources
> that were used to make the new box.

Well that all depends on the load. Recently we moved two low-load 
machines into a virtual environment, perhaps we didn't cut the 
power/cooling costs in half, but it's certainly an improvement.

> 
> Let's say you're running 4 copies of Windows, in VMs, on a host copy
> of Windows. That's 5 gig of RAM and 4,500MHz of CPU bandwidth blown on
> all those copies of Windows, of which 4.5GB and 4000MHz are running
> duplicated code that is shared by all the VMs.

In this case I agree that virtualization is probably a bad idea. But if 
the client OS needs 250MB worth of memory and a few percent of the CPU. 
You could easily squeeze three of them into 1GB (asuming the host OS 
needs only 250 MB, which might be optimistic). Also think of the case 
where the client systems doesn't need the CPU all the time.

> 
> If, instead, you were running an OS that could partition itself so
> that the 4 workloads all ran on the same shared kernel, but completely
> isolated from one another, so that one could have one version of the
> core libraries and another a different version, 

This would be awsome, is there any such system? My guess is that it is 
very hard to get right. However you totally miss the case where you need 
different operating systems.

> Does that make my point clear?

Yes, I see that there are cases where virtualization is really stupid. 
But I hope that my argumentation for the cases where it is smart make 
sense :)


Cheers,
Pontus.