Ceph block storage interacts directly with RADOS and a separate daemon is therefore not required (unlike CephFS and RGW). A Ceph block device is known as a RADOS Block Device (or simply an RBD device) and is available from a newly deployed Ceph cluster. This also makes RBD highly available by default.
RBD client usage
This section will provide optional instructions for verifying the RBD service by setting up a simple client environment. Deploy the client using the steps provided in the Client setup appendix.
An example deployment will have a juju status output similar to the following:
Model Controller Cloud/Region Version SLA Timestamp
ceph my-controller my-maas/default 2.8.1 unsupported 19:34:16Z
App Version Status Scale Charm Store Rev OS Notes
ceph-client 20.04 active 1 ubuntu jujucharms 15 ubuntu
ceph-mon 15.2.3 active 3 ceph-mon jujucharms 49 ubuntu
ceph-osd 15.2.3 active 3 ceph-osd jujucharms 304 ubuntu
Unit Workload Agent Machine Public address Ports Message
ceph-client/0* active idle 3 10.0.0.240 ready
ceph-mon/0 active idle 0/lxd/1 10.0.0.247 Unit is ready and clustered
ceph-mon/1 active idle 1/lxd/1 10.0.0.242 Unit is ready and clustered
ceph-mon/2* active idle 2/lxd/1 10.0.0.249 Unit is ready and clustered
ceph-osd/0 active idle 0 10.0.0.229 Unit is ready (2 OSD)
ceph-osd/1* active idle 1 10.0.0.230 Unit is ready (2 OSD)
ceph-osd/2 active idle 2 10.0.0.252 Unit is ready (2 OSD)
The client host is represented by the ceph-client/0 unit.
Create a Ceph pool (‘libvirt-pool’), an RBD user (‘client.libvirt’), collect the user’s keyring file, and transfer it to the client:
juju run-action --wait ceph-mon/0 create-pool name=libvirt-pool app-name=rbd
juju run --unit ceph-mon/0 -- \
sudo ceph auth get-or-create client.libvirt \
mon 'profile rbd' osd 'profile rbd pool=libvirt-pool' | \
tee ceph.client.libvirt.keyring
juju scp ceph.client.libvirt.keyring ceph-client/0:
Connect to the client:
juju ssh ceph-client/0
From the RBD client,
Configure the client using the keyring file and set up the correct permissions:
sudo mv ~ubuntu/ceph.client.libvirt.keyring /etc/ceph
sudo chmod 600 /etc/ceph/ceph.client.libvirt.keyring
sudo chown ubuntu: /etc/ceph/ceph.client.libvirt.keyring
Install the requisite image creation software and verify that an RBD image can be created:
sudo apt install -y qemu-utils
qemu-img create -f raw rbd:libvirt-pool/image-4d:id=libvirt 4G
From the Juju client,
RBD images/pools can be inspected by querying the cluster with various commands:
juju ssh ceph-mon/0 sudo rbd -p libvirt-pool ls
juju ssh ceph-mon/0 sudo rados df --pool libvirt-pool