From 8314ca9c101aefab186d72420a42d15125bc3598 Mon Sep 17 00:00:00 2001 From: Aaron Lauterer Date: Tue, 21 Jul 2020 11:54:35 +0200 Subject: [PATCH] docs: fix #2851 Add note about GC grace period Adding a note about the garbage collection's grace period due to the default atime behavior should help to avoid confusion as to why space is not freed immediately. Signed-off-by: Aaron Lauterer --- docs/administration-guide.rst | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/docs/administration-guide.rst b/docs/administration-guide.rst index 254d36e1..a0ac8c79 100644 --- a/docs/administration-guide.rst +++ b/docs/administration-guide.rst @@ -962,6 +962,17 @@ unused data blocks are removed. depending on the number of chunks and the speed of the underlying disks. +.. note:: The garbage collection will only remove chunks that haven't been used + for at least one day (exactly 24h 5m). This grace period is necessary because + chunks in use are marked by touching the chunk which updates the ``atime`` + (access time) property. Filesystems are mounted with the ``relatime`` option + by default. This results in a better performance by only updating the + ``atime`` property if the last access has been at least 24 hours ago. The + downside is, that touching a chunk within these 24 hours will not update its + ``atime`` property. + + If there are chunks in the grace period, it will be logged at the end of the + garbage collection run as *Pending removals*. .. code-block:: console