diff --git a/sysinv/sysinv/sysinv/sysinv/api/controllers/v1/ceph_mon.py b/sysinv/sysinv/sysinv/sysinv/api/controllers/v1/ceph_mon.py
index dc0cdfe8ed..b24fa5c4da 100644
--- a/sysinv/sysinv/sysinv/sysinv/api/controllers/v1/ceph_mon.py
+++ b/sysinv/sysinv/sysinv/sysinv/api/controllers/v1/ceph_mon.py
@@ -308,7 +308,13 @@ class CephMonController(rest.RestController):
                 if rpc_cephmon.ceph_mon_gib != p['value']:
                     is_ceph_mon_gib_changed = True
 
-        if not is_ceph_mon_gib_changed:
+        # TODO This should be removed after resize operation is supported in AIO-DX systems
+        if is_ceph_mon_gib_changed and cutils.is_aio_duplex_system(pecan.request.dbapi):
+            raise exception.CephCommandUnsupported(
+                _("Resize of ceph monitor is not allowed in duplex system.")
+            )
+
+        elif not is_ceph_mon_gib_changed:
             LOG.info("ceph_mon parameters are not changed")
             raise wsme.exc.ClientSideError(
                 _("Warning: ceph_mon parameters are not changed."))
diff --git a/sysinv/sysinv/sysinv/sysinv/common/exception.py b/sysinv/sysinv/sysinv/sysinv/common/exception.py
index 2707c36a70..f110ecdb1a 100644
--- a/sysinv/sysinv/sysinv/sysinv/common/exception.py
+++ b/sysinv/sysinv/sysinv/sysinv/common/exception.py
@@ -235,6 +235,11 @@ class CephPoolSetParamFailure(CephFailure):
                 "Reason: %(reason)s")
 
 
+class CephCommandUnsupported(CephFailure):
+    # 503 means service unavailable which seems appropriate for commands that are unsupported
+    code = 503
+
+
 class InvalidCPUInfo(Invalid):
     message = _("Unacceptable CPU info") + ": %(reason)s"