[libvirt PATCH 1/2] docs: kbase: Add a doc on live full disk backup

[Peter Krempa]

On Tue, May 04, 2021 at 18:16:12 +0200, Kashyap Chamarthy wrote:
> This is a rewrite of:
> 
>     https://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit
> 
> Once this commit merges, the above wiki should point to this kbase
> document.
> 
> Signed-off-by: Kashyap Chamarthy <kchamart at redhat.com>
> ---
>  docs/kbase/index.rst                 |   3 +
>  docs/kbase/live_full_disk_backup.rst | 111 +++++++++++++++++++++++++++
>  2 files changed, 114 insertions(+)
>  create mode 100644 docs/kbase/live_full_disk_backup.rst

[...]

> diff --git a/docs/kbase/live_full_disk_backup.rst b/docs/kbase/live_full_disk_backup.rst
> new file mode 100644
> index 0000000000..f4ef7f2cc7
> --- /dev/null
> +++ b/docs/kbase/live_full_disk_backup.rst
> @@ -0,0 +1,111 @@
> +Efficient live full disk backup
> +===============================

It feels nowadays a bit weird to add a document which outlines
everything you can achieve with the virDomainBackupBegin API without any
of the extra steps.

I'd suggest you note that this predates the backup APIs or link to them
somehow.


> +
> +Overview
> +--------
> +
> +Live full disk backups are preferred in many scenarios, *despite* their
> +space requirements.  The following outlines an efficient method to do
> +that using libvirt's APIs.  This method involves concepts: the notion of
> +`backing chains <https://libvirt.org/kbase/backing_chains.html>`_,
> +`QCOW2 overlays
> +<https://qemu.readthedocs.io/en/latest/interop/live-block-operations.html#disk-image-backing-chain-notation>`_,
> +and a special operation called "active block-commit", which allows
> +live-merging an overlay disk image into its backing file.