[libvirt] need some help/asdive

[Gene Czarcinski]

Background:

I am a newbie to Linux Virtualization.

However, I have been using Linux for a long time.  After a short time with 
Slackware, I started with Red Hat Linux 2 and went on to 2.1, 3.0.3, 4, 4.2, 
5, 5.2, ..., 8, 9.  And then on to Fedora Core 1, 2, ... until I installed 
Fedora 11 about a month ago.

I have also run VMware starting when it first appeared.  Initially I used 
VMware to run Windows.  These days I use it to run up to from 25 to 30 guests 
(between 1 and 5 at the same time) [yes, I have lots of system memory].  

Besides a couple of Windows guests, I have some guests supporting both 32 bit 
(i386) and 64 bit (x86_64) architectures of older releases as well as 
alternatives such as CentOS -- I use these to build RPMs.  Then there are the 
guests supporting other operating systems such as Solaris and *BSD.  Finally, 
I have a set of test guest that I use for testing stuff which could destroy the 
operating system or which require a lot of re-booting.  All of this in 25 to 
30 guests.

With Fedora 11, I started by trying VMware-server.  Server 1.0.9 (which I used 
on Fedora 9) looks like much more work to get running ... more or less "a 
bridge too far".  So, I tried server 2.0.2 ... but the client interface 
changed from a separate GUI application to a browser based interface: 1) this 
impacts my usage of the firefox browser; 2) it is a buggy implementation; and 
3) it is a crappy interface which I do not like.

So, I (finally) noticed that Linux in general and Fedora specifically has 
packages supporting running guests virtually ... so, lets change my "problem 
sets" and give this a try ... especially when I noticed that it could use the 
hardware support in my new AMD Phenom II 940 processor.

Before getting into my specific questions/problem, let me describe how my 
systems are set up.  First of all, I have a basic rule: "don't screw with a 
working system."  Therefore, on each of my systems I have at least two root 
partitions defined -- one for the current (working) system and one for the next 
(new) system [these days it is actually a /boot partition with root being on a 
striped logical volume].  I also have a small (think minimal install) 
partition with Fedora to serve as a boot selector (using chainloader), as 
something to to define striped logical volumes, and to be there for "emergency" 
maintenance.  Guys, this works for me and always doing fresh installs saves on 
other headaches.

Implicit in the above is that I put all of my data and my /home into separate 
partitions or logical volumes.  One of these are my VMware guest systems.  Now 
VMware puts all of the files (configuration, disk image, etc.) associated a 
guest under a separate directory.  Fedora virtualization does not do this and 
separation is something I need so that I can easily move to a new version of 
the operating system such as when Fedora 12 becomes available in November.

Questions/problems:

My first question:  it appears to me that a guest is defined by two things -- a 
configuration file in /etc/libvirt/qemu and one or more disk images in 
/var/lib/libvirt/images ... is this it or are there other files I need to 
consider?

My second question concerns the location of the disk images:  what is the 
"best practical way" to move these out of the root partition?  I have come up 
with these different approaches which could/may work:

1. change the "path" value in /etc/libvirt/storage/default.xml to point to a 
directory in a different partition.

2. Use a /etc/fstab entry to "bind mount" a directory in a separate partition 
onto /var/lib/libvirt/images

3. Just use an /etc/fstab entry to mount a partition on 
/var/lib/libvirt/images or, perhaps, on /var/lib/libvirt. [This could be done 
during system installation]

OK, any comments on these??

I can live with changing some configuration files, I can live with copying guest 
configuration files between systems, I CANNOT live with the disk image files 
being put into the root partition.  Before jumping "whole hog" into using 
Fedora Virtualization in place of VMware, I need to be able to live with the 
result.  Figure 30 guest virtuals with 10GB of virtual disk each, that is 
300GB.  I have that space but not for every root partition on my system!

Comment:  It sure would be nice if Fedora Virtualization put all files related 
to a guest under a single directory the way VMware does.

Comment:  It sure would be nice if there was some system-wide configuration 
parameter that defined where virtualization files went.

Right now, as a newbie, I am using the virt-manage GUI interface.  I am 
studying the command-line programs to see what they offer me.

So far, I like what I see in Fedora Virtualization but I need to address how 
things will be practically managed sooner rather than later.

Any help appreciated.

Gene