doc/PendingReleaseNotes: document osd_scrub_queued_snaptrims_limit

osd_scrub_queued_snaptrims_limit, introduced in PR#68737,
blocks the initiation of non-urgent scrubs on OSDs that
are overloaded with snap-trim operations.

Signed-off-by: Ronen Friedman <rfriedma@redhat.com>

diff --git a/PendingReleaseNotes b/PendingReleaseNotes
index 98002ebad0f218db0a52afce0cc886fe6a6a0327..a3ec1db9ec6ec97e429ddfb5c1b768814db80d9d 100644 (file)
--- a/PendingReleaseNotes
+++ b/PendingReleaseNotes
@@ -43,6 +43,13 @@
   and the scrubbing process is delayed between each read in order to avoid monopolizing
   the I/O capacity of the OSD.
   The default stride size (``osd_deep_scrub_stride``) was 512 KBytes, and is now 4 MBytes.
+* RADOS: When an OSD is overloaded with queued snap-trim operations, no
+  regular (non-urgent) scrubs will be scheduled on that OSD. This is
+  determined by comparing the total snap-trim queue lengths for all PGs
+  for which the OSD is a primary against ``osd_scrub_queued_snaptrims_limit``,
+  which defaults to 500.
+  This restriction does not apply to operator-initiated scrubs, nor to repair scrubs.
+  It can be disabled by setting ``osd_scrub_queued_snaptrims_limit`` to 0.
 
 * RADOS: Stretch mode can now be entered even if the two dividing buckets differ
   in weight by a small fraction (default 0.1). This is tunable via