diff --git a/ci/environments/scenario004-multinode-containers.yaml b/ci/environments/scenario004-multinode-containers.yaml
index 6a7206611a..028654935a 100644
--- a/ci/environments/scenario004-multinode-containers.yaml
+++ b/ci/environments/scenario004-multinode-containers.yaml
@@ -101,7 +101,11 @@ parameter_defaults:
     journal_size: 512
     journal_collocation: true
     osd_scenario: collocated
-  CephPoolDefaultPgNum: 32
+  # Without MDS and RGW we create 5 pools, totalling 160 PGs at 32 PGs each
+  # With MDS and RGW instead we create 9 pools, so we lower the PG size
+  CephPoolDefaultPgNum: 16
+  ManilaCephFSDataPoolPGNum: 16
+  ManilaCephFSMetadataPoolPGNum: 16
   CephPoolDefaultSize: 1
   CephAnsibleExtraConfig:
     centos_package_dependencies: []
diff --git a/environments/low-memory-usage.yaml b/environments/low-memory-usage.yaml
index 07b27b1579..a4d3d9296a 100644
--- a/environments/low-memory-usage.yaml
+++ b/environments/low-memory-usage.yaml
@@ -20,6 +20,8 @@ parameter_defaults:
 
   # Override defaults to get HEALTH_OK with 1 OSD (for testing only)
   CephPoolDefaultSize: 1
-  CephPoolDefaultPgNum: 32
+  CephPoolDefaultPgNum: 16
+  ManilaCephFSDataPoolPGNum: 16
+  ManilaCephFSMetadataPoolPGNum: 16
 
   NovaReservedHostMemory: 512