diff --git a/qa/tasks/cephfs/test_exports.py b/qa/tasks/cephfs/test_exports.py
index e5ad18dd662a2..ba71bba024b07 100644
--- a/qa/tasks/cephfs/test_exports.py
+++ b/qa/tasks/cephfs/test_exports.py
@@ -153,6 +153,8 @@ def getlrg():
         # vstart.sh sets mds_debug_subtrees to True. That causes a ESubtreeMap
         # to be written out every event. Yuck!
         self.config_set('mds', 'mds_debug_subtrees', False)
+        # make sure ESubtreeMap is written frequently enough:
+        self.config_set('mds', 'mds_log_minor_segments_per_major_segment', '4')
         self.config_rm('mds', 'mds bal split size') # don't split /top
         self.mount_a.run_shell_payload("rm -rf 1")
 
diff --git a/src/common/options/mds.yaml.in b/src/common/options/mds.yaml.in
index 94824faef6bcf..8263554524b17 100644
--- a/src/common/options/mds.yaml.in
+++ b/src/common/options/mds.yaml.in
@@ -1739,4 +1739,4 @@ options:
   default: 16
   services:
   - mds
-  min: 8
+  min: 4