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Add a Ceph Cluster

Onboard an existing Ceph cluster as a storage backend for VM disks (RBD), so multiple compute nodes can read/write the same volumes for live migration and HA.

Prerequisites

  • A healthy Ceph cluster (ceph -s reports HEALTH_OK).
  • Network reachability from every compute node to MON IPs on 3300/tcp + 6789/tcp and OSD IPs on 6800-7300/tcp.
  • A Ceph user with read/write access to the pool you'll use — typically client.libvirt.
# On a Ceph MON, create an MFCloud-scoped user:
ceph auth get-or-create client.libvirt \
    mon 'profile rbd' \
    osd 'profile rbd pool=mfcloud' \
    mgr 'profile rbd pool=mfcloud'

# Capture the key — you'll paste it into the UI:
ceph auth get-key client.libvirt

Quick steps

  1. Settings → Ceph Clusters → + Add Cluster.
  2. Fill in:
  3. Cluster Name — friendly label (e.g. ceph-primary).
  4. Monitor IP(s) — comma-separated list of MON addresses.
  5. Pool — the RBD pool name (mfcloud in the example above).
  6. Client User — libvirt (no client. prefix in the field).
  7. Admin Key — the key from ceph auth get-key above.
  8. Save & Test. MFCloud will:
  9. Store the key in the ceph_clusters table.
  10. Generate a libvirt secret on every Active node with virsh secret-define/virsh secret-set-value.
  11. Probe MON reachability and refuse the row if it can't connect.

Once Ceph appears in the Storage picker on the Create VM modal, the cluster is wired.

Pool sizing reference

Pool size OSDs needed Use case
size=2 2+ Lab / cost-sensitive (data loss possible on dual failure).
size=3 3+ Production default — survives one OSD failure with no degraded reads.
EC 4+2 6+ Cold-ish data, ~33 % storage overhead vs size=3's 200 %.

Set with:

ceph osd pool set mfcloud size 3 --yes-i-really-mean-it

Removing a cluster

Settings → Ceph Clusters → row → Remove. The libvirt secret is undefined on every node and the row is dropped. VM disks that live on this Ceph pool are not deleted — rbd ls -p mfcloud will still show them and you can recover by re-adding the same cluster.

See also