[ceph-users] What affection to vm with Monitor down

Hi,everyone Our production ceph cluster the version is hammer have 3 monitors and 300+ osds.Monitor daemon runs on host diffrent from osd daemon. openstack vm runs on rbd.Now we need to maintain monitor host so must shutdown monitor host a moment, one by one. But keep two monitor host online all the time. What is the impact of monitor down on vm? How to do reduce the impact?