[dba-Tech] Question about VMs

[John Colby]

Arthur,

It is "fundamentally backwards".  It is possible to run a Hypervisor, 
which is a thin layer of software that fields all of the I/O, memory and 
cpu requests from virtual machines and map them to actual (shared) 
hardware.  That is what Windows Hyper-V is.  VMWare has a similar 
setup.  Linux does as well AFAIK.  I have only ever used MS Hyper-V, but 
I have run that for many years.

Just as an example, I run a 6 core AMD processor with 32 gigs of ram.  I 
have Hyper-V installed.  Hyper-v runs an instance of Windows 2008, which 
is essentially just another virtual machine, but that instance is a 
virtual machine controller (kinda).  It is a full on Windows 2008 server 
instance, running on top of Hyper-V and whose primary job is to allow me 
to run tools to manage my "real" virtual machines.  I then have about 8 
virtual machines available, although I only run 6 of them.  All of these 
VMs run Windows 2011, which is Windows Home Server (WHS), which is 
actually a slightly modified Windows 2008.  All of the above are X64 
machines.  I actually installed all of my software and then cloned that 
VM to make the others.  A non-trivial task at least the way I did it.

So the Windows 2008 VM server instance (running on the hypervisor) 
allows me to set up, start, stop, update and so forth all of the virtual 
machines.  It is quite literally a VM Server supervisor.  Understand 
though that the virtual machines do NOT run "inside" of that instance of 
windows, the VMs all run on the hypervisor, which is as close to "bare 
metal" as it is possible to get.  It is just that Windows has magically 
allowed this 2008 instance to "see" and manage the VMs themselves with 
tools that DO run inside of that 2008 instance.

The 2008 VM Server also can and does run an instance of SQL Server.  For 
no particular reason, just because I wanted it to.

Each of my WHS 2011 VMs has up to 4 logical cores, but actually run 2 
logical cores.  Each VM can have as much memory as the physical server 
minus a few gigs, but in fact that would potentially cause extensive 
paging and so I actually limit them to 4 gigs, simply because that is 
all that is needed.  So the memory they are assigned is pretty much real 
memory, but the cores and the rest of the "hardware" of the VM is an 
emulated machine.

Really cool if you think about it.


On 9/13/2016 8:19 PM, Arthur Fuller wrote:
> Although I've been using Oracle VirtualBox for years, I confess that I have
> very little knowledge as to how this stuff works. It all seems to be inside
> out to me. First I have to run Windows or Linux and then run VirtualBox and
> then run one of my VMs, and this seems fundamentally backwards to me. As I
> see it with these increasing bad eyes, the first thing that should boot is
> the VM manager, and then let me select which VM(s) I want to run.
>
> Is there a product that takes that approach? Or if not, why not? What am I
> missing here?
>
> It might seem that multi-boot is a if not The solution, but over the years
> I have had dozens of problems trying to set up a machine to multi-boot. It
> would appear that my principal villain is Grub, which keeps screwing up my
> boxes and then I have to devote another weekend to buying flowers, begging,
> and replacing her entire wardrobe.
>
> Maybe my problem is that I begin with a Windows box, and then try some
> other OSes atop that. Maybe I should just do a White Wedding all over that
> box and Start Again, making the Ubuntu installation my Main Squeeze, and
> and then seeing if she will allow me to have a few Virtual Mistresses (VMs,
> in case you're not following my leaps from metaphor to metaphor).
>

-- 
John W. Colby