Ceph

We are running a three-node Ceph cluster on riboflavin, ginkgo and biloba for the purpose of cloud storage. Most Ceph services are running on riboflavin or ginkgo; biloba is just providing a tiny bit of extra storage space.

Official documentation: https://docs.ceph.com/en/latest/

At the time this page was written, the latest version of Ceph was 'Pacific'; check the website above to see what the latest version is.

Bootstrap

The instructions below were adapted from https://docs.ceph.com/en/pacific/cephadm/install/.

riboflavin was used as the bootstrap host, since it has the most storage.

Add the following to /etc/apt/sources.list.d/ceph.list:

deb http://mirror.csclub.uwaterloo.ca/ceph/debian-pacific/ bullseye main

Download the Ceph release key for the Debian packages:

wget -O /etc/apt/trusted.gpg.d/ceph.release.gpg https://download.ceph.com/keys/release.gpg

Now run:

apt update
apt install cephadm podman
ceph boostrap --mon-ip 172.19.168.25

For the rest of the instructions below, the ceph command can be run inside a Podman container by running cephadm shell. Alternatively, you can install the ceph-common package to run ceph directly on the host.

Add the disks for riboflavin:

ceph orch daemon add osd riboflavin:/dev/sdb
ceph orch daemon add osd riboflavin:/dev/sdc

Note: Unfortunately Ceph didn't like it when I used one of the /dev/disk/by-id paths, so I had to use the /dev/sdX paths instead. I'm not sure what'll happen if the device names change at boot. Let's just cross our fingers and pray.

Add more hosts:

ceph orch host add ginkgo 172.19.168.22 --labels _admin
ceph orch host add biloba 172.19.168.23

Add each available disk on each of the additional hosts.

Disable unnecessary services:

ceph orch rm alertmanager
ceph orch rm grafana
ceph orch rm node-exporter

Set the autoscale profile to scale-up instead of scale-down:

ceph osd pool set autoscale-profile scale-up

Set the default pool replication factor to 2 instead of 3:

ceph config set global osd_pool_default_size 2

Deploy the Managers and Monitors on riboflavin and ginkgo only:

ceph orch apply mon --placement '2 riboflavin ginkgo'
ceph orch apply mgr --placement '2 riboflavin ginkgo'

CloudStack Primary Storage

We are using RBD (RADOS Block Device) for CloudStack primary storage. The instructions below were adapted from https://docs.ceph.com/en/pacific/rbd/rbd-cloudstack/.

Create and initialize a pool:

ceph osd pool create cloudstack
rbd pool init cloudstack

Create a user for CloudStack:

ceph auth get-or-create client.cloudstack mon 'profile rbd' osd 'profile rbd pool=cloudstack'

Make a backup of this key. There is currently a copy in /etc/ceph/ceph.client.cloudstack.keyring on biloba. If you want to use the ceph command with this set of credentials, use the -n flag, e.g.

ceph -n client.cloudstack status

RBD commands

Here are some RBD commands which might be useful:

• List images (i.e. block devices) in the cloudstack pool:

  rbd ls -p cloudstack
  

• View snapshots for an image:

  rbd snap ls cloudstack/265dc008-4db5-11ec-b585-32ee6075b19b
  

• Unprotect a snapshot:

  rbd snap unprotect cloudstack/265dc008-4db5-11ec-b585-32ee6075b19b@cloudstack-base-snap
  

• Purge all snapshots for an image (after unprotecting them):

  rbd snap purge cloudstack/265dc008-4db5-11ec-b585-32ee6075b19b
  

• Delete an image:

  rbd rm cloudstack/265dc008-4db5-11ec-b585-32ee6075b19b
  

• A quick 'n dirty script to delete all images in the pool:

  rbd ls -p cloudstack | while read image; do rbd snap unprotect cloudstack/$image@cloudstack-base-snap; done
  rbd ls -p cloudstack | while read image; do rbd snap purge cloudstack/$image; done
  rbd ls -p cloudstack | while read image; do rbd rm cloudstack/$image; done