Infrastructure.Next 2015, Ghent, Belgium
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Title
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Advanced manipulation of virtual machine snapshots and disk images with
libvirt and QEMU


Abstract
--------

Over the past couple of years, there have been a number of incremental
improvements in virtualization infrastructure projects like libvirt and
QEMU to manage and manipulate virtual machine snapshots and disk image
chains in libvirt. QEMU allows the notion of backing files, i.e. you can
create a delta (or overlay) images on top of a base image (the backing
file), often called a template or master image.


A practical scenario: Managing QEMU overlay-based snapshots can become
cumbersome over the period of time.  With each new snapshot, a new QCOW2
overlay file is created, resulting in the adminstrative overhead of
tracking multiple disk image files.  Understanding the ability to manage
multiple disk image files/external snapshots (in libvirt parlance)
efficiently will help alleviate this overhead.

This session aims to discuss some of the new advances in livirt and QEMU
that address this need of advanced disk image management. Specific
topics include -- shortening disk image chains, offline and online
snapshot merging, live merge an entire disk image chain, live disk
mirroring (optionally pivoting live QEMU to this just mirrored disk
copy), applying and deleting snapshots.

The combination of libvirt API, QEMU and KVM hypervisor is one of the
widely deployed virtualization drivers in OpenStack. So, we'll also
see how some of these concepts are used in the context of OpenStack
Compute project (Nova).

This session includes a brief demonstration of some of the mechansisms
discussed.


Audience
--------

Audience would include virtualization and infrastructure software
administrators, tinkerers or developers. Or anyone curious about
KVM/QEMU/libvirt-based virtualization software.


References
----------

- https://kashyapc.fedorapeople.org/virt/lcco-2014/
- http://kashyapc.fedorapeople.org/virt/lc-2012/lceu-2012-virt-snapshots-kashyap-chamarthy.pdf 
- https://kashyapc.fedorapeople.org/virt/lcco-2014/Update-on-QEMU-and-libvirt-snapshots-disk-image-chains-CloudOpen-Eu-2014.pdf
- http://wiki.libvirt.org/page/Live-merge-an-entire-disk-image-chain-including-current-active-disk
- http://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit