Adding new servers to Proxmox/Ceph cluster cannot access the Shared RBD datastore

[cryptworks]

I have been working with Proxmox and Ceph and have really liked both in combination. However I have run into a stumbling block and really do not know what my next steps are.

Issue I am running into:

5 server Proxmox cluster All Fenced, All Configured in Ceph. All working beautifully.
Add 2 new servers to the cluster, they joined the cluster and seem ot be reasonably happy, i was able to join them as Ceph monitors, and that works great, but the RBD datastore comes up with the festive rbd error: rbd: couldn't connect to the cluster! (500). I have no added any OSD's on these new servers as they are not meant to host anything. but i did like the additional information adding them as a ceph monitor, wich is why i did it.

What i want to know is where i can look to get more details as to WHY it is failing? I really would like to work this out (its educational) but i am running out of ideas where ot find the reason they cannot connect to the ceph pool, because everything ceph related i can do from the CLI works fine.

 

[cryptworks]

So I found my own Solution, I still do not know where these errors would be logged so if someone can help me with that it would be great.

So my answer was a footnote on this page, https://pve.proxmox.com/wiki/Storage:_Ceph

[h=2]Manual configuration edit[/h] edit your /etc/pve/storage.cfg and add the configuration 
 rbd: mycephcluster
       monhost 192.168.0.1:6789;192.168.0.2:6789;192.168.0.3:6789
       pool rbd  (optional, default =r rbd)
       username admin (optional, default = admin)
       content images
note: you must use ip (not dns fqdn) for monhost

The last line "note: you must use ip (not dns fqdn) for monhost" manually made the edit to change from fqdn to IP and it started working across all hosts.

So aside fome being able to find error logging can anyone tell me why this fails, and why i would need to use Ip over fqdn? and why it would work then not work?