[Cialug] Next AmesLUG topic

[Daniel A. Ramaley]

On 2010-09-14 at 17:05:55, murraymckee at wellsfargo.com wrote:
>Why would you chose one VM over another?

Different virtual machine technologies are suited for different tasks. I 
help maintain the Xen cluster at work, but use VirtualBox on my personal 
machines. Xen is very well-suited to large installations that are 
running many VMs as always-on servers, VirtualBox is well-suited to 
running the occasional VM on my desktop (great for testing and for the 
errant Windows app).

For the remainder of these questions, i'll assume we are talking about 
desktop-side virtualization (VirtualBox, Parallels, VMWare Workstation, 
ec.) since that seems to suit your level of knowledge better. (Please 
pardon the presumption... or if not, feel free to flame me.) If you want 
to discuss server-side virtualization (Xen, KVM, VMWare Server), then 
most of these answers would be very different.

>	What are the strong & weak points of the various VMs?

Mostly this would depend on if you're talking desktop or server style 
virtualization. Within those 2 spheres, however, strong & weak points 
tend to be similar.

Some VM architectures have more overhead than others, or allow VMs to 
run faster than others. Or support different operating systems (either 
for host or guest). Or are Free versus proprietary. If you have 
something specific in mind that you want to do, i'm sure someone could 
recommend a good VM architecture to start with. Personally i'd recommend 
VirtualBox since it is easy to install and the documentation is easy to 
follow (read the entire User Manual... it's worth the time to gain 
understanding how VM stuff works).

>What do they cost to install?  Purchase price / disk space / etc.

Depends on which one. Some are free. Disk space for the VM architecture 
itself is usually minimal on modern hardware (a few MB to a couple GB).

>What do they cost to run?  CPU / Memory / etc.

The VM software itself doesn't use much in the way of resources. The VMs 
running within it, however, will certainly need some CPU and RAM. My 
machine at work has a dual-core CPU with 4 GB RAM. At home i have a 
dual-core with 8 GB RAM. I've never had any problem running several VMs 
on either machine, though if i have the VMs doing any serious number 
crunching i'd probably want more CPU available.

>How do you install it?  Guest OS and then VM or vice versa

Most desktop VM architectures install like any other application. Many 
install kernel drivers which may or may not require a reboot, depending 
on which host OS you're on.

For a desktop VM architecture, you install your host OS first, then the 
VM software, then whatever guest OSes you intend to use.

>Any special considerations to installing an OS as a guest rather than
>a base OS?

If you're installing something esoteric, check the compatibility list 
for the VM software first. If your guest OS is not listed, that doesn't 
mean you are out of luck, just that you're diving into uncharted waters. 
Check online forums (as always, Google is your friend) to see if anyone 
else has installed the same OS and what (if anything) they had to do 
special.

If installing something common (Windows XP or higher, Linux with a 2.6 
kernel), you'll probably have no trouble. Read the documentation 
though--you might have to install a small tools package into the guest 
OS so that it performs better.

>How do you start a VM with a guest OS?

In VirtualBox, you launch the VirtualBox application, then select which 
VM you want to run, and click the start button for that VM. Other 
desktop VM architectures are probably similar. In other words: easy.

>How do you run multiple guests of the same OS?

Create multiple VMs. (If virtualizing an OS that is somewhat piggish in 
its use of resources *Windows* *cough* *cough* then plan on having lots 
of free disk space to create the VMs and lots of RAM if you want to run 
more than one at a time.)

>How do you run multiple guests of different OSs?

Create multiple VMs.

>How do you divide up the disk space for the different guests?

However you want. When you create a VM, you'll be asked how much disk to 
allocate to it. In your host OS the VM's disk will appear either as a 
single large file, or a few smaller files of some small number of GB 
each.

>Can the VM run off the C drive and guest 1 think that the D drive is
>its C and guest 2 think that the E drive is its C?

>Can the C drive be partitioned and a different partition given to each
>guest as its C drive?

OK, now we know that you're planning on running Windows as the host OS.

Unless i'm misunderstanding, these 2 are the same question, just phrased 
slightly differently. So i'll answer both at once:

This should be possible (depending on which VM architecture you choose), 
but generally is considered a very advanced way to set things up. 
Normally, each VM's disk is just a file on the host OS, not a partition. 
If you don't have enough space on C: for your VM disks, you should be 
able to put them somewhere else. Non-Windows VMs usually only need a few 
GB disk space.

>How can files be shared between guests if needed?

Most VM architectures allow you to mount part of the host filesystem as 
a network drive. Usually you have to install some small tools first, but 
it is all pretty easy to setup. If the VM software doesn't make it easy, 
you could use whatever file sharing the guests support: NFS, CIFS, etc.

>How do you switch the video and keyboard between guests or do you need
>to have one for each guest? If so, how do you connect multiple videos
>and keyboards to a computer?

On desktop virtualization, the guest appears in a window on your 
desktop. To switch to it, you either just move the mouse over it, or (at 
worst) have to click in the window.

>How do you maintain the VM? Install patches, update apps, etc.

Do you mean the VM software itself? Same as any other software. You 
either apply updates when they come out. Or you don't. Up to you. If 
you're guest OS is something that has proper package management (such as 
most Linuxes), then you don't have to worry about it--the package 
manager will apply updates when/if they are available.

>How do you maintain the guest OSs?

Same as you do when they are running on bare hardware.

>How do I let the system know that the USB device plugged into that
>port needs to be connected to guest X?

The VM software should provide a way to do this. If that is important to 
you, look for that feature when choosing which VM software to go with. I 
know the non-Free version of VirtualBox will do this, and it is free.

>Can I switch a USB port between guests as necessary, or once it's
>assigned is it stuck, until I reboot, forever, etc. ?

You should be able to switch.

>Are there any special considerations for living in the country and only
>having dial up access?

Setting up networking on the VMs might be more interesting, but 
basically, no.

>And then there is the ultimate question, what don't I know about VMs
>that I should know?

I'd suggest downloading and installing some VM software. Then install a 
guest OS or two (or three). Play with the software. Read the 
documentation. Those are the best ways to get used to the concepts of 
how it all works.

>Or is there a book that I should be reading instead of tying up
>meeting time?

I haven't read any dead-tree books on virtualization. But most of the 
software comes with detailed PDF documentation. Reading some of that 
will help your understanding.
__
Daniel A. Ramaley
Network Engineer 2

Dial Center 118, Drake University
2407 Carpenter Ave / Des Moines IA 50311 USA
Tel: +1 515 271-4540
Fax: +1 515 271-1938
E-mail: daniel.ramaley at drake.edu