[clug] Virt-Manager & snapshots Vs Xen

[George at Clug]

I was using KVM with Virt-Manager under Centos 7 and Debian Wheezy and
when I went to take a snapshot of a 6 TB server before applying
updates, and found that there was no snapshot support. For me
snapshots are a base requirement for any virtual machine. For example,
before applying any updates to a virtual server, take snapshot,
install updates, test running software to see nothing as broken,
delete snapshot while consoldiating image, or if the changes cause
issues, roll back the image to the snapshot and live without the
updates until you can apply them without causing issues.

Searching on the Internet I discovered that Virt-Manager >= version
1.0 can take snapshots if the image is qcow2.

http://blog.wikichoon.com/2014/03/snapshot-support-in-virt-manager.html
The biggest feature we added in virt-manager 1.0 is VM snapshot
support. ... Only works with qcow2 disk images. ... While the overlay
files have to be qcow2, these snapshots will work with any base disk
image. They can also be performed with very little VM downtime, at
least under a second. 

When checking both Debian Jessie and CentOS 7, I discovered that
Virt-Manager was < version 1.0, so using standard packages was not
going to be a useful solution. I will be pleased with these OSs
upgrade to a virt-manager that can support snapshots,but it could be a
long while away.

Going to the Virt-Manager home page, I downloaded the latest verison
of the source code, "virt-manager 1.1.0 Sunday September 07, 2014", 
http://virt-manager.org/download/


"To build an RPM, you can run:    python setup.py rpm"
When I attempted to compile an RPM for CentOS 7, the compile failed
with "Requires: libosinfo >= 0.2.10".


ftp://ftp.isu.edu.tw/pub/Linux/Fedora/linux/releases/test/21-Alpha/Workstation/x86_64/os/Packages/l/libosinfo-0.2.11-1.fc21.x86_64.rpm
http://pkgs.org/fedora-21/fedora-x86_64/libosinfo-0.2.11-2.fc21.x86_64.rpm.html
http://dl.fedoraproject.org/pub/fedora/linux/development/21/x86_64/os/Packages/l/libosinfo-0.2.11-2.fc21.x86_64.rpm

The above provided an RPM for libosinfo which allowed Virt-Manager to
compile.

Now I if I create a qcow2 based virtual machine, I can take snapshots,
though I have not yet had time to test the stability or effectiveness
of these snapshots.

I would be interested in peoples comments on the above.

I originaly dismissed Xen as I believed it was tied to a commercial
company, and not completely open to the Open Source community.  If I
am wrong please correct me. Also let me know what type of management
interface Xen can use.
http://en.wikipedia.org/wiki/Xen
The Xen community develops and maintains Xen as free and open-source
software, subject to the requirements of the GNU General Public
License (GPL), version 2.