[pbs-devel] [PATCH proxmox-backup v2 3/3] docs: add garbage collection timing example

[Fabian Grünbichler]

On April 5, 2024 3:05 pm, Hannes Duerr wrote:
> To make the garbage collection process easier to understand, we add a
> timing example with a graphic.
> 
> Signed-off-by: Hannes Duerr <h.duerr at proxmox.com>
> ---
>  docs/images/garbage-collection-timing.svg | 2513 +++++++++++++++++++++
>  docs/maintenance.rst                      |   25 +
>  2 files changed, 2538 insertions(+)
>  create mode 100644 docs/images/garbage-collection-timing.svg
> 
> diff --git a/docs/images/garbage-collection-timing.svg b/docs/images/garbage-collection-timing.svg
> new file mode 100644
> index 00000000..8108ee23
> --- /dev/null
> +++ b/docs/images/garbage-collection-timing.svg

[snip]

> diff --git a/docs/maintenance.rst b/docs/maintenance.rst
> index e25c8f19..a23e5c21 100644
> --- a/docs/maintenance.rst
> +++ b/docs/maintenance.rst
> @@ -233,6 +233,31 @@ by the GC as it cannot be certain whether they are still needed.
>     which is 24 hours by default.
>  
>  
> +Timing Example
> +^^^^^^^^^^^^^^
> +
> +.. figure:: images/garbage-collection-timing.svg
> +  :class: proxmox-svg
> +  :alt: Garbage Collection timing
> +
> +t\ :sub:`0`\:
> +All chunks are part of the backup indices. Some chunks have a newer
> +``atime`` than the cut-off time, while others have not been accessed
> +for a while (e.g. because they were only created by a new backup).
> +
> +t\ :sub:`1`\:
> +A backup has been deleted and some chunks are no longer used
> +
> +t\ :sub:`2`\:
> +The first phase of the GC begins and the ``atime`` of the chunks that
> +are still being used by a backup are updated
> +
> +t\ :sub:`3`\:
> +The second phase of the GC begins. Chunks that have not been used and
> +whose ``atime`` is older than the cut-off time are deleted. Chunks that
> +have not been used but whose ``atime`` is newer than the cut-off time
> +are not yet deleted, but are marked as pending as a precaution.

I think a visualization might help understand how GC, backup tasks and
pruning interact. I am not sure this one is "it", though ;)

Maybe changing the time to flow downwards would give more space in the
horizontal axis to display indices and chunks at a certain point in
time? At least for me, the arrangement of the chunks between the time
markers throws me off..

> +
>  Manually Starting GC
>  ^^^^^^^^^^^^^^^^^^^^
>  
> -- 
> 2.39.2
> 
> 
> 
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> 
> 
>