Monitors are not required for accessing data from the Ceph cluster.
Clients will ask a monitor for a current OSD map and then use that OSD map
to communicate with the OSDs directly for all reads and writes.  The map
includes the crush map which has all of the information a client needs to
know where every object is in the cluster.  Having 3 mons is a good number
for small deployments.  5 mons is better for better redundancy in the
monitor quorum.  Avoid an even number of mons always.

librbd is definitely the way to go for accessing RBDs for a hypervisor as
opposed to fuse or krbd.  For a quick and easy hypervisor using Ceph, I
like Proxmox.  It natively has the ability to use KVM with Ceph without
having to configure it yourself.  It comes with a nice gui as well to see
the console screen for your VMs.  It also has a fairly simple guide to
cluster hypervisors together to provide HA support for your VMs.  For
larger scale VM deployments, Openstack is probably the way I would go.

On Tue, Feb 13, 2018 at 2:11 PM Egoitz Aurrekoetxea <>

> Good afternoon,
> As I'm new to Ceph I was wondering what could be the most proper way to
> use it with Xen hypervisor (with a plain Linux installation, Centos, for
> instance). Have read the less proper one is to just
> mount the /dev/rbdX device in a mount point and just showing that space
> to the Hypervisor but I see it pretty easy and seems stable. Seems not
> to perform bad... Is it better to use for instance librbd
> with KVM?. Does it perform better?.
> By the way, it seems to use the monitor node in order to access to the
> space in the osd cluster. Have read too that Ceph has been designed
> keeping in mind no single points of failure but... is it possible
> to configure several monitor nodes, and then after a very little timeout
> or similar to access to the file system through the other nodes?. What
> could be the most proper way of configuring this for avoiding a
> machine to loose the storage if the monitor fails?. Could you point
> please me in the right direction?. Perhaps with several monitors or....
> By the way if you could consider it would be better to use another
> hypervisor or config (with librados or whatever) with Ceph, could you
> please suggest me too?. Help to the newbie :p :) :)
> Best regards,
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