i am using ceph-deploy to deploy ceph cluster. after deployment is finished, i found the runtime config is not the same with ceph.conf. i did not modify the runtime config in manual.

```
[root@sz02 ~]# ceph daemon osd.0 config show | grep rbd_cache
"rbd_cache": "true",
"rbd_cache_writethrough_until_flush": "true",
"rbd_cache_size": "33554432",
"rbd_cache_max_dirty": "25165824",
"rbd_cache_target_dirty": "16777216",
"rbd_cache_max_dirty_age": "1",
"rbd_cache_max_dirty_object": "0",
"rbd_cache_block_writes_upfront": "false",
[root@sz02 ~]# cat /etc/ceph/ceph.conf | grep "rbd cache size"
rbd cache size = 268435456

```

we can see that rbd\_cache\_size is different. so i want to know: 

whether ceph runtime config reads the value from ceph.conf or not? if not, what's the meaning of ceph.conf?

thanks