Rook Add-On

The Rook add-on creates and manages a Ceph cluster along with a storage class for provisioning PVCs. It also runs the Ceph RGW object store to provide an S3-compatible store in the cluster.

By default the cluster uses the filesystem for storage. Each node in the cluster will have a single OSD backed by a directory in /opt/replicated/rook. Nodes with a Ceph Monitor also utilize /var/lib/rook.

Note: At minimum, 10GB of disk space should be available to /var/lib/rook for the Ceph Monitors and other configs. We recommend a separate partition to prevent a disruption in Ceph's operation as a result of /var or the root partition running out of space.

The EKCO add-on is recommended when installing Rook. EKCO is responsible for performing various operations to maintain the health of a Ceph cluster.

Advanced Install Options

spec:
  rook:
    version: latest
    blockDeviceFilter: sd[b-z]
    cephReplicaCount: 3
    isBlockStorageEnabled: true
    storageClassName: "storage"
    hostpathRequiresPrivileged: false
    bypassUpgradeWarning: false

Flag	Usage
version	The version of rook to be installed.
storageClassName	The name of the StorageClass that will use Rook to provision PVCs.
cephReplicaCount	Replication factor of ceph pools. The default is to use the number of nodes in the cluster, up to a maximum of 3.
isBlockStorageEnabled	Use block devices instead of the filesystem for storage in the Ceph cluster.
isSharedFilesystemDisabled	Disable the rook-ceph shared filesystem, reducing CPU and Memory load by no longer needing to schedule several pods. 1.4.3+
blockDeviceFilter	Only use block devices matching this regex.
hostpathRequiresPrivileged	Runs Ceph Pods as privileged to be able to write to hostPaths in OpenShift with SELinux restrictions.
bypassUpgradeWarning	Bypass upgrade warning prompt.

Block Storage

For production clusters, Rook should be configured to use block devices rather than the filesystem. Enabling block storage is required with version 1.4.3+. The following spec enables block storage for the Rook add-on and automatically uses disks matching the regex /sd[b-z]/. Rook will start an OSD for each discovered disk, which could result in multiple OSDs running on a single node.

spec:
  rook:
    version: latest
    isBlockStorageEnabled: true
    blockDeviceFilter: sd[b-z]

The Rook add-on will wait for a disk before continuing. If you have attached a disk to your node but the installer is still waiting at the Rook add-on installation step, refer to the troubleshooting guide for help with diagnosing and fixing common issues.

Shared Filesystem

The Ceph filesystem is supported with version 1.4.3+. This allows the use of PersistentVolumeClaims with access mode ReadWriteMany. Set the storage class to rook-cephfs in the pvc spec to use this feature.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: cephfs-pvc
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
  storageClassName: rook-cephfs