Re: [pve-devel] [PATCH pve-docs] vzdump: add section describing PBS change detection mode

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On June 26, 2024 10:13 am, Christian Ebner wrote:
> Add a concise section about what PBS change detection mode is and
> what it affects, including a table with a description of the modes.
> 
> Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
> ---
>  vzdump.adoc | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/vzdump.adoc b/vzdump.adoc
> index 79d4bbc..958ee12 100644
> --- a/vzdump.adoc
> +++ b/vzdump.adoc
> @@ -171,6 +171,30 @@ fleecing image up-front. On a thinly provisioned storage, the fleecing image can
>  grow to the same size as the original image only if the guest re-writes a whole
>  disk while the backup is busy with another disk.
>  
> +CT Change Detection Mode
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Setting the change detection mode defines the encoding format for the pxar
> +archives and how changed and unchanged files are handled for container backups
> +with Proxmox Backup Server as target.
> +
> +Backups of VMs or to other storage backends are not affected by this setting.
> +
> +There are 3 change detection modes available:
> +
> +[width="100%",cols="<m,4d",options="header"]
> +|===============================================================================
> +| Mode     | Description
> +| Default  | The legacy mode, read and encode all files in a self contained
> +pxar archive with format version 1 being uploaded to the Proxmox Backup Server.

I'd shorten this:

Read and encode all files into a single archive, using the pxar format
version 1.

> +| Data     | (EXPERIMENTAL): Read and encode all files, but split data and
> +metadata into separate streams, using the pxar format version 2.
> +| Metadata | (EXPERIMENTAL): Use the metadata archive of the previous backup
> +run to detect unchanged files and reuse the files data already backed up in the
> +previous backup for the current backup run when possible. Data and metadata are
> +encoded into separate streams, using the pxar format version 2.

Split streams and archive format version 2 like `Data`, but use metadata
archive of previous snapshot (if one exists) to detect unchanged files,
and reuse their data chunks without reading file contents from disk,
whenever possible.

This is easier to parse (I hope) and both explains the difference to
`Data`, and the reason why you'd want to use it ;)

> +|===============================================================================
> +
>  Backup File Names
>  -----------------
>  
> -- 
> 2.39.2
> 
> 
> 
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> 
> 


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