See what the Ceph client sees
The title is probably weird and misleading but I could not find better than this :). The idea here is to dive a little bit into what the kernel client sees for each client that has a RBD device mapped. In this article, we are focusing on the Kernel RBD feature.
In order to see things, you need to adjust some debug values.
So you need to add the following into your
[mon] ... debug ms = 1 ... [osd] ... debug ms = 1
Then you can create and map a device like so:
$ rbd create foo -s 10240
Since we increased the debug level, you should now have noticed that we have a client directory in
$ sudo ls /sys/kernel/debug/ceph/dee72d38-cd8b-42c1-93c1-3be0698206ca.client24166/
So as you see we have several crucial information that the client will use to interact with the cluster. Important files such as the OSD map are present:
$ sudo cat /sys/kernel/debug/ceph/dee72d38-cd8b-42c1-93c1-3be0698206ca.client24166/osdmap
And the monitors map:
$ sudo cat /sys/kernel/debug/ceph/dee72d38-cd8b-42c1-93c1-3be0698206ca.client24166/monmap