Re: [pbs-devel] [PATCH v2 proxmox-backup 2/2] docs: deduplicate background details for garbage collection

[Gabriel Goller <g.goller@proxmox.com>]

On 14.11.2024 10:47, Christian Ebner wrote:
>On 11/14/24 10:39, Gabriel Goller wrote:
>>On 13.11.2024 16:55, Christian Ebner wrote:
>>>diff --git a/docs/maintenance.rst b/docs/maintenance.rst
>>>index e8a26d69c..bba3feff4 100644
>>>--- a/docs/maintenance.rst
>>>+++ b/docs/maintenance.rst
>>>@@ -197,6 +197,8 @@ It's recommended to setup a schedule to ensure 
>>>that unused space is cleaned up
>>>periodically. For most setups a weekly schedule provides a good 
>>>interval to
>>>start.
>>>
>>>+.. _gc_background:
>>>+
>>>GC Background
>>>^^^^^^^^^^^^^
>>>
>>>@@ -222,17 +224,31 @@ datastore or interfering with other backups.
>>>The garbage collection (GC) process is performed per datastore and 
>>>is split
>>>into two phases:
>>>
>>>-- Phase one: Mark
>>>-  All index files are read, and the access time of the referred 
>>>chunk files is
>>>-  updated.
>>>-
>>>-- Phase two: Sweep
>>>-  The task iterates over all chunks, checks their file access 
>>>time, and if it
>>>-  is older than the cutoff time (i.e., the time when GC started, 
>>>plus some
>>>-  headroom for safety and Linux file system behavior), the task 
>>>knows that the
>>>-  chunk was neither referred to in any backup index nor part of 
>>>any currently
>>>-  running backup that has no index to scan for. As such, the 
>>>chunk can be
>>>-  safely deleted.
>>>+- Phase one (Mark):
>>>+
>>>+  All index files are read, and the access time (``atime``) of 
>>>the referenced
>>>+  chunk files is updated.
>>>+
>>>+- Phase two (Sweep):
>>>+
>>>+  The task iterates over all chunks and checks their file access 
>>>time against a
>>>+  cutoff time. The cutoff time is given by either the oldest 
>>>backup writer
>>>+  instance, if present, or 24 hours and 5 minutes after the start 
>>>of garbage
>>>+  collection.
>>>+
>>
>>>+  Garbage collection can consider chunk files with access time 
>>>older than the
>>
>>s/can consider/considers/
>
>Acked!
>
>>It always considers chunks with atime older than cutoff to be dangling
>>afaik.
>This part here is referring to the second phase, so cleaning up the 
>chunks. Or what do you mean here by dangling?

Yep that's what I meant, the gc *must* consider these chunks, it's not
optional – so no 'can'.

>>>+  cutoff time to be neither referenced by any backup snapshot's 
>>>index, nor part
>>>+  of any currently running backup job. Therefore, these chunks 
>>>can safeley be
>>>+  deleted.
>>
>>s/safeley/safely/
>
>Acked!

Oh and consider:

Reviewed-by: Gabriel Goller <g.goller@proxmox.com>

for both patches!


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