Document scrubbing behavior

Signed-off-by: David Zafman <david.zafman@inktank.com>

diff --git a/doc/dev/osd_internals/scrub.rst b/doc/dev/osd_internals/scrub.rst
new file mode 100644 (file)
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+++ b/doc/dev/osd_internals/scrub.rst
@@ -0,0 +1,30 @@
+
+Scrubbing Behavior Table
+========================
+
++-------------------------------------------------+----------+-----------+---------------+----------------------+
+|                                          Flags  | none     | noscrub   | nodeep_scrub  | noscrub/nodeep_scrub |
++=================================================+==========+===========+===============+======================+
+| Periodic tick                                   |   S      |    X      |     S         |         X            |
++-------------------------------------------------+----------+-----------+---------------+----------------------+
+| Periodic tick after osd_deep_scrub_interval     |   D      |    D      |     S         |         X            |
++-------------------------------------------------+----------+-----------+---------------+----------------------+
+| Initiated scrub                                 |   S      |    S      |     S         |         S            |
++-------------------------------------------------+----------+-----------+---------------+----------------------+
+| Initiated scrub after osd_deep_scrub_interval   |   D      |    D      |     S         |         S            |
++-------------------------------------------------+----------+-----------+---------------+----------------------+
+| Initiated deep scrub                            |   D      |    D      |     D         |         D            |
++-------------------------------------------------+----------+-----------+---------------+----------------------+
+
+- X = Do nothing
+- S = Do regular scrub
+- D = Do deep scrub
+
+State variables
+---------------
+
+- Periodic tick state is !must_scrub && !must_deep_scrub && !time_for_deep 
+- Periodic tick after osd_deep_scrub_interval state is !must_scrub && !must_deep_scrub && time_for_deep 
+- Initiated scrub state is  must_scrub && !must_deep_scrub && !time_for_deep
+- Initiated scrub after osd_deep_scrub_interval state is must scrub && !must_deep_scrub && time_for_deep
+- Initiated deep scrub state is  must_scrub && must_deep_scrub