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

[Hannes Dürr]

On 4/8/24 11:35, Fabian Grünbichler wrote:
> 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..

As discussed offlist, a possible compromise would be to split the 
graphics into 3 with

descriptive text in between to make it clear that the graphics represent 
a moment

during a phase.

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