[lug] Virtualization w/Windows host, was something else

[Chip Atkinson]

On Sun, 29 Nov 2009, karl horlen wrote:

<snip>
> 
> in terms of virtualization, what do you mean by snapshots?  i understand the concept in terms of a backup but not sure how it relates to vms.
ots are essentially copies of the vm file(s) at the moment they are
taken.

Snapshots are essentially copies of the vm files that are made at the
moment the snapshot is taken.  They are handy for times when you wish to
try some sort of configuration or upgrade, etc.  You take the snapshot,
make your changes and see what you think.  If it's broken, you just revert
to snapshot and you are back as if the changes were never made.

> 
> SOME OTHER GENERAL VIRT QUESTIONS
> 
> also, after looking at some online virtualization documentation, this
> stuff appears easier than i thought.  i originally thought you had to
> work a lot of magic to make an non virtual os host a virtual host os
> but it appears you simply
> 
> a) download a pkg or executable (for windows) and install the sucker and fire it up
> 
> b) you create your vdisk for your guest
> 
> c) start up the guest and install to it
> 
> Q1] 
> 
> simple. are these pretty universal install and config procedures for
the plethora of virtualization options that exist out there today?

I've only used vmware and virtualbox, but yes, that's exactly it.  The VM
"thing" is just a program that emulates a hardware machine.  It's pretty
sophisticated internally but it runs just like any other program runs.

 > 
> Q2]
> 
> i get the impression most of these options are pretty robust these
> days.  after all some have been out for quite a long time.  last thing
> i'd want to do is setup virtualization and muck up my system.  can
> someone confirm the *general* robustness of these suckers today and
> when and if something goes wrong, what percentage usually gets borked
> : the host, the guest, both, etc?  is it something you can usually
> recover from.  i guess i'd be ok if my guest got borked but i
> definitely wouldn't want my host OS to get hosed.

I've been really pleased with the results myself.  VMWare is heavily used
in the QA world because it does a very good job at acting like hardware
and is pretty easy to deal with.  I have had an iPod hang virtualbox
when I tried to get it to be seen by the virtual machine manager.  I
finally had to reboot windows (the host) and everything started up just
fine.  

When doing QA work I've heard vmware get blamed for some odd behavior.
Further investigation showed it was just a cop-out and vmware was fully
exonerated.

 > 
> Q3]
> 
> when you install virtualization sw on a host, if you don't start up a
> guest vm are you still incurring a performance penalty hit?  i'm
> assuming this stuff is running at the kernel level, even in scnearios
> where from what i can tell the guest is HW virtualization.  if there
> is a performance or resource hit from a vm host not running any
> guests, how minimal is it?  does it eat up a lot of ram and cpu cycles
> or is some percentage say 90% only when the guest vm starts up?  
> looking for generalizations / rough estimates here.

Not too much.  It's the guest that does the slowing down.  You can run
vmware or virtualbox as a reguar user IIRC.  It's not a very significant
impact performance wise when there's nothing on it.
 > 
> Q4]
> 
> finally, as i reacquaint myself with virtualization, can someone
> clarify the virtualization networking term which is used to describe
> the scenario where you want a guest's network interface to look like
> it's on the same external lan it's host is connected to?  sort of like
> they're peers to the corp internal lan.  is that what's known as
> 'bridging'?  this will help me google come network configuration time.

Yes, that's bridging.  The advantage is that you can see the virtual
machine from the corp. network.  The disadvantage is that you can be seen
on the corp. network. 

The other two options are NAT which makes all your traffic look like it's
coming from the host, and internal, where all traffic is contained within
the vm.  It's good for setting up test networks with several VMs.

> 
> i think the virtualization networking scenarios and terms are what
> confused me with virtualization a couple of years ago.  if anybody has
> a link to good explanations of virtual networking terms and scenarios
> that'd be greatly appreciated.
> 
> thanks
> 
> 
>       
> _______________________________________________
> Web Page:  http://lug.boulder.co.us
> Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
> Join us on IRC: lug.boulder.co.us port=6667 channel=#hackingsociety
>