docs: update docs with WOSD3 and WOSD4

Signed-off-by: Alfredo Deza <[email protected]>

docs/source/codes/osds.rst

@@ -24,3 +24,24 @@ WOSD2
 Setting ``osd pool default min size = 1`` can lead to data loss because if the
 minimum is not met, Ceph will not acknowledge the write to the client.
 
+.. _WOSD3:
+
+WOSD3
+^^^^^
+The default value of 3 OSD nodes for a healthy cluster must be met. If
+``ceph.conf`` is configured to a different number, that setting will take
+precedence. The number of OSD nodes is calculated by adding
+``osd_pool_default_size`` and ``osd_pool_default_min_size`` + 1. By default,
+this adds to 3.
+
+.. _WOSD4:
+
+WOSD4
+^^^^^
+If ratios have been modified from its defaults, a warning is raised pointing to
+any ratio that diverges. The ratios observed with their defaults are:
+
+* ``backfillfull_ratio``: 0.9
+* ``nearfull_ratio``: 0.85
+* ``full_ratio``: 0.95
+