Ceph Cluster CRD

Rook allows creation and customization of storage clusters through the custom resource definitions (CRDs).

Sample

To get you started, here is a simple example of a CRD to configure a Ceph cluster with all nodes and all devices. More examples are included later in this doc.

NOTE In addition to your CephCluster object, you need to create the namespace, service accounts, and RBAC rules for the namespace you are going to create the CephCluster in. These resources are defined in the example common.yaml.

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    # see the "Cluster Settings" section below for more details on which image of ceph to run
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  storage:
    useAllNodes: true
    useAllDevices: true

Settings

Settings can be specified at the global level to apply to the cluster as a whole, while other settings can be specified at more fine-grained levels. If any setting is unspecified, a suitable default will be used automatically.

Cluster metadata

• name: The name that will be used internally for the Ceph cluster. Most commonly the name is the same as the namespace since multiple clusters are not supported in the same namespace.
• namespace: The Kubernetes namespace that will be created for the Rook cluster. The services, pods, and other resources created by the operator will be added to this namespace. The common scenario is to create a single Rook cluster. If multiple clusters are created, they must not have conflicting devices or host paths.

Cluster Settings

• cephVersion: The version information for launching the ceph daemons.
  • image: The image used for running the ceph daemons. For example, ceph/ceph:v12.2.9-20181026 or ceph/ceph:v13.2.2-20181023. For the latest ceph images, see the Ceph DockerHub. To ensure a consistent version of the image is running across all nodes in the cluster, it is recommended to use a very specific image version. Tags also exist that would give the latest version, but they are only recommended for test environments. For example, the tag v13 will be updated each time a new mimic build is released. Using the v13 or similar tag is not recommended in production because it may lead to inconsistent versions of the image running across different nodes in the cluster.
  • allowUnsupported: If true, allow an unsupported major version of the Ceph release. Currently only luminous and mimic are supported, so nautilus would require this to be set to true. Should be set to false in production.
• dataDirHostPath: The path on the host (hostPath) where config and data should be stored for each of the services. If the directory does not exist, it will be created. Because this directory persists on the host, it will remain after pods are deleted.
  • On Minikube environments, use /data/rook. Minikube boots into a tmpfs but it provides some directories where files can be persisted across reboots. Using one of these directories will ensure that Rook’s data and configuration files are persisted and that enough storage space is available.
  • WARNING: For test scenarios, if you delete a cluster and start a new cluster on the same hosts, the path used by dataDirHostPath must be deleted. Otherwise, stale keys and other config will remain from the previous cluster and the new mons will fail to start. If this value is empty, each pod will get an ephemeral directory to store their config files that is tied to the lifetime of the pod running on that node. More details can be found in the Kubernetes empty dir docs.
• dashboard: Settings for the Ceph dashboard. To view the dashboard in your browser see the dashboard guide.
  • enabled: Whether to enable the dashboard to view cluster status
  • urlPrefix: Allows to serve the dashboard under a subpath (useful when you are accessing the dashboard via a reverse proxy)
  • port: Allows to change the default port where the dashboard is served
  • ssl: Whether to serve the dashboard via SSL, ignored on Ceph versions older than 13.2.2
• network: The network settings for the cluster
  • hostNetwork: uses network of the hosts instead of using the SDN below the containers.
• mon: contains mon related options mon settings For more details on the mons and when to choose a number other than 3, see the mon health design doc.
• rbdMirroring: The settings for rbd mirror daemon(s). Configuring which pools or images to be mirrored must be completed in the rook toolbox by running the rbd mirror command.
  • workers: The number of rbd daemons to perform the rbd mirroring between clusters.
• annotations: annotations configuration settings
• placement: placement configuration settings
• resources: resources configuration settings
• storage: Storage selection and configuration that will be used across the cluster. Note that these settings can be overridden for specific nodes.
  • useAllNodes: true or false, indicating if all nodes in the cluster should be used for storage according to the cluster level storage selection and configuration values. If individual nodes are specified under the nodes field below, then useAllNodes must be set to false.
  • nodes: Names of individual nodes in the cluster that should have their storage included in accordance with either the cluster level configuration specified above or any node specific overrides described in the next section below. useAllNodes must be set to false to use specific nodes and their config. See node settings below.
  • config: Config settings applied to all OSDs on the node unless overridden by devices or directories. See the config settings below.
  • storage selection settings

Mon Settings

• count: Set the number of mons to be started. The number should be odd and between 1 and 9. If not specified the default is set to 3 and allowMultiplePerNode is also set to true.
• preferredCount: If you want to increase the number of mons when the number of nodes increases, set the preferredCount to be larger than the count. For example, if your cluster starts with three nodes, but might grow to more than five nodes, you might want five mons running after the other nodes come online. In this case, set count: 3 and preferredCount: 5. When the operator sees the new nodes come online, the number of mons will increase to the preferred count. If the number of nodes decreases below the preferredCount, the operator will reduce the number of mons back to count. If allowMultiplePerNode: true (for testing scenarios), the number of mons will always use preferredCount if set.
• allowMultiplePerNode: Enable (true) or disable (false) the placement of multiple mons on one node. Default is false.

If these settings are changed in the CRD the operator will update the number of mons during a periodic check of the mon health, which by default is every 45 seconds.

To change the defaults that the operator uses to determine the mon health and whether to failover a mon, the following environment variables can be changed in operator.yaml. The intervals should be small enough that you have confidence the mons will maintain quorum, while also being log enough to ignore network blips where mons are failed over too often.

• ROOK_MON_HEALTHCHECK_INTERVAL: The frequency with which to check if mons are in quorum (default is 45 seconds)
• ROOK_MON_OUT_TIMEOUT: The interval to wait before marking a mon as “out” and starting a new mon to replace it in the quroum (default is 600 seconds)

Node Settings

In addition to the cluster level settings specified above, each individual node can also specify configuration to override the cluster level settings and defaults. If a node does not specify any configuration then it will inherit the cluster level settings.

• name: The name of the node, which should match its kubernetes.io/hostname label.
• config: Config settings applied to all OSDs on the node unless overridden by devices or directories. See the config settings below.
• storage selection settings

When useAllNodes is set to true, Rook attempts to make Ceph cluster management as hands-off as possible while still maintaining reasonable data safety. If a usable node comes online, Rook will begin to use it automatically. To maintain a balance between hands-off usability and data safety, Nodes are removed From Ceph as OSD hosts only (1) if the node is deleted from Kubernetes itself or (2) if the node has its taints or affinities modified in such a way that the node is no longer usable by Rook. Any changes to taints or affinities, intentional or unintentional, may affect the data reliability of the Ceph cluster. In order to help protect against this somewhat, deletion of nodes by taint or affinity modifications must be “confirmed” by deleting the Rook-Ceph operator pod and allowing the operator deployment to restart the pod.

For production clusters, we recommend that useAllNodes is set to false to prevent the Ceph cluster from suffering reduced data reliability unintentionally due to a user mistake. When useAllNodes is set to false, Rook relies on the user to be explicit about when nodes are added to or removed from the Ceph cluster. Nodes are only added to the Ceph cluster if the node is added to the Ceph cluster resource. Similarly, nodes are only removed if the node is removed from the Ceph cluster resource.

Node Updates

Nodes can be added and removed over time by updating the Cluster CRD, for example with kubectl -n rook-ceph edit cephcluster rook-ceph. This will bring up your default text editor and allow you to add and remove storage nodes from the cluster. This feature is only available when useAllNodes has been set to false.

Storage Selection Settings

Below are the settings available, both at the cluster and individual node level, for selecting which storage resources will be included in the cluster.

• useAllDevices: true or false, indicating whether all devices found on nodes in the cluster should be automatically consumed by OSDs. Not recommended unless you have a very controlled environment where you will not risk formatting of devices with existing data. When true, all devices will be used except those with partitions created or a local filesystem. Is overridden by deviceFilter if specified.
• deviceFilter: A regular expression that allows selection of devices to be consumed by OSDs. If individual devices have been specified for a node then this filter will be ignored. This field uses golang regular expression syntax. For example:
  • sdb: Only selects the sdb device if found
  • ^sd.: Selects all devices starting with sd
  • ^sd[a-d]: Selects devices starting with sda, sdb, sdc, and sdd if found
  • ^s: Selects all devices that start with s
  • ^[^r]: Selects all devices that do not start with r
• devices: A list of individual device names belonging to this node to include in the storage cluster.
  • name: The name of the device (e.g., sda).
  • config: Device-specific config settings. See the config settings below.
• directories: A list of directory paths that will be included in the storage cluster. Note that using two directories on the same physical device can cause a negative performance impact.
  • path: The path on disk of the directory (e.g., /rook/storage-dir).
  • config: Directory-specific config settings. See the config settings below.
• location: Location information about the cluster to help with data placement, such as region or data center. This is directly fed into the underlying Ceph CRUSH map. The type of this field is string. For example, to add datacenter location information, set this field to rack=rack1. More information on CRUSH maps can be found in the ceph docs.

OSD Configuration Settings

The following storage selection settings are specific to Ceph and do not apply to other backends. All variables are key-value pairs represented as strings.

• metadataDevice: Name of a device to use for the metadata of OSDs on each node. Performance can be improved by using a low latency device (such as SSD or NVMe) as the metadata device, while other spinning platter (HDD) devices on a node are used to store data.
• storeType: filestore or bluestore, the underlying storage format to use for each OSD. The default is set dynamically to bluestore for devices, while filestore is the default for directories. Set this store type explicitly to override the default. Warning: Bluestore is not recommended for directories in production. Bluestore does not purge data from the directory and over time will grow without the ability to compact or shrink.
• databaseSizeMB: The size in MB of a bluestore database. Include quotes around the size.
• walSizeMB: The size in MB of a bluestore write ahead log (WAL). Include quotes around the size.
• journalSizeMB: The size in MB of a filestore journal. Include quotes around the size.
• osdsPerDevice**: The number of OSDs to create on each device. High performance devices such as NVMe can handle running multiple OSDs. If desired, this can be overridden for each node and each device.
• encryptedDevice**: Encrypt OSD volumes using dmcrypt (“true” or “false”). By default this option is disabled. See http://docs.ceph.com/docs/nautilus/ceph-volume/lvm/encryption/ for more information on encryption in Ceph.

** NOTE: Depending on the Ceph image running in your cluster, OSDs will be configured differently. Newer images will configure OSDs with ceph-volume, which provides support for osdsPerDevice, encryptedDevice, as well as other features that will be exposed in future Rook releases. OSDs created prior to Rook v0.9 or with older images of Luminous and Mimic are not created with ceph-volume and thus would not support the same features. For ceph-volume, the following images are supported:

• Luminous 12.2.10 or newer
• Mimic 13.2.3 or newer
• Nautilus

Annotations Configuration Settings

Annotations can be specified so that the Rook components will have those annotations added to them.

You can set annotations for Rook components through the a list of key value pairs:

• all: Set annotations for all components.
• mgr: Set annotations for MGRs.
• mon: Set annotations for Mons.
• osd: Set annotations for OSDs.
• rbdmirror: Set annotations for RBD Mirrors.

When other keys are set, all will be merged together with the specific component.

Placement Configuration Settings

Placement configuration for the cluster services. It includes the following keys: mgr, mon, osd, rbdmirror and all. Each service will have its placement configuration generated by merging the generic configuration under all with the most specific one (which will override any attributes).

A Placement configuration is specified (according to the kubernetes PodSpec) as:

• nodeAffinity: kubernetes NodeAffinity
• podAffinity: kubernetes PodAffinity
• podAntiAffinity: kubernetes PodAntiAffinity
• tolerations: list of kubernetes Toleration

The mon pod does not allow Pod affinity or anti-affinity. This is because of the mons having built-in anti-affinity with each other through the operator. The operator chooses which nodes are to run a mon on. Each mon is then tied to a node with a node selector using a hostname. See the mon design doc for more details on the mon failover design.

The Rook Ceph operator creates a Job called rook-ceph-detect-version to detect the full Ceph version used by the given cephVersion.image. The placement from the mon section is used for the Job.

Cluster-wide Resources Configuration Settings

Resources should be specified so that the Rook components are handled after Kubernetes Pod Quality of Service classes. This allows to keep Rook components running when for example a node runs out of memory and the Rook components are not killed depending on their Quality of Service class.

You can set resource requests/limits for Rook components through the Resource Requirements/Limits structure in the following keys:

• mgr: Set resource requests/limits for MGRs.
• mon: Set resource requests/limits for Mons.
• osd: Set resource requests/limits for OSDs.
• rbdmirror: Set resource requests/limits for RBD Mirrors.

In order to provide the best possible experience running Ceph in containers, Rook internally enforces minimum memory limits if resource limits are passed. Basically, if a user configures a limit or request value that is too low Rook will refuse to run the pod(s). Here are the current minimum amounts of memory in MB to apply so that Rook will accept to run Ceph pods:

• mon: 1024MB
• mgr: 512MB
• osd: 4096MB
• mds: 4096MB
• rbdmirror: 512MB

Resource Requirements/Limits

For more information on resource requests/limits see the official Kubernetes documentation: Kubernetes - Managing Compute Resources for Containers

• requests: Requests for cpu or memory.
  • cpu: Request for CPU (example: one CPU core 1, 50% of one CPU core 500m).
  • memory: Limit for Memory (example: one gigabyte of memory 1Gi, half a gigabyte of memory 512Mi).
• limits: Limits for cpu or memory.
  • cpu: Limit for CPU (example: one CPU core 1, 50% of one CPU core 500m).
  • memory: Limit for Memory (example: one gigabyte of memory 1Gi, half a gigabyte of memory 512Mi).

Samples

Here are several samples for configuring Ceph clusters. Each of the samples must also include the namespace and corresponding access granted for management by the Ceph operator. See the common cluster resources below.

Storage configuration: All devices

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  dashboard:
    enabled: true
  # cluster level storage configuration and selection
  storage:
    useAllNodes: true
    useAllDevices: true
    deviceFilter:
    location:
    config:
      metadataDevice:
      databaseSizeMB: "1024" # this value can be removed for environments with normal sized disks (100 GB or larger)
      journalSizeMB: "1024"  # this value can be removed for environments with normal sized disks (20 GB or larger)
      osdsPerDevice: "1"

Storage Configuration: Specific devices

Individual nodes and their config can be specified so that only the named nodes below will be used as storage resources. Each node’s ‘name’ field should match their ‘kubernetes.io/hostname’ label.

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  dashboard:
    enabled: true
  # cluster level storage configuration and selection
  storage:
    useAllNodes: false
    useAllDevices: false
    deviceFilter:
    location:
    config:
      metadataDevice:
      databaseSizeMB: "1024" # this value can be removed for environments with normal sized disks (100 GB or larger)
      journalSizeMB: "1024"  # this value can be removed for environments with normal sized disks (20 GB or larger)
    nodes:
    - name: "172.17.4.101"
      directories:         # specific directories to use for storage can be specified for each node
      - path: "/rook/storage-dir"
    - name: "172.17.4.201"
      devices:             # specific devices to use for storage can be specified for each node
      - name: "sdb"
      - name: "sdc"
      config:         # configuration can be specified at the node level which overrides the cluster level config
        storeType: bluestore
    - name: "172.17.4.301"
      deviceFilter: "^sd."

Storage Configuration: Cluster wide Directories

This example is based up on the Storage Configuration: Specific devices. Individual nodes can override the cluster wide specified directories list.

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  dashboard:
    enabled: true
  # cluster level storage configuration and selection
  storage:
    useAllNodes: false
    useAllDevices: false
    config:
      databaseSizeMB: "1024" # this value can be removed for environments with normal sized disks (100 GB or larger)
      journalSizeMB: "1024"  # this value can be removed for environments with normal sized disks (20 GB or larger)
    directories:
    - path: "/rook/storage-dir"
    nodes:
    - name: "172.17.4.101"
      directories: # specific directories to use for storage can be specified for each node
      # overrides the above `directories` values for this node
      - path: "/rook/my-node-storage-dir"
    - name: "172.17.4.201"

Node Affinity

To control where various services will be scheduled by kubernetes, use the placement configuration sections below. The example under ‘all’ would have all services scheduled on kubernetes nodes labeled with ‘role=storage’ and tolerate taints with a key of ‘storage-node’.

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  # enable the ceph dashboard for viewing cluster status
  dashboard:
    enabled: true
  placement:
    all:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: role
              operator: In
              values:
              - storage-node
      tolerations:
      - key: storage-node
        operator: Exists
    mgr:
      nodeAffinity:
      tolerations:
    mon:
      nodeAffinity:
      tolerations:
    osd:
      nodeAffinity:
      tolerations:

Resource Requests/Limits

To control how many resources the Rook components can request/use, you can set requests and limits in Kubernetes for them. You can override these requests/limits for OSDs per node when using useAllNodes: false in the node item in the nodes list.

WARNING Before setting resource requests/limits, please take a look at the Ceph documentation for recommendations for each component: Ceph - Hardware Recommendations.

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  # enable the ceph dashboard for viewing cluster status
  dashboard:
    enabled: true
  # cluster level resource requests/limits configuration
  resources:
  storage:
    useAllNodes: false
    nodes:
    - name: "172.17.4.201"
      resources:
        limits:
          cpu: "2"
          memory: "4096Mi"
        requests:
          cpu: "2"
          memory: "4096Mi"

Custom Location Information On Node Level

For each individual node a location can be configured. The provided information is fed directly into the CRUSH map of Ceph. More information on CRUSH maps can be found in the ceph docs.

HINT When setting this prior to CephCluster creation, these settings take immediate effect. However, applying this to an already deployed CephCluster requires to remove each node from the cluster first and then re-add it with new configuration to take effect. Do this node by node to keep your data safe! You can check the result with ceph osd tree from the Rook Toolbox in your setup. The OSD tree should display your location hierarchy for the nodes you already re-added.

This example assumes you have 3 unique racks in your datacenter and want to use them as failure domain

apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: ceph/ceph:v14.2.1-20190430
  dataDirHostPath: /var/lib/rook
  mon:
    count: 3
    allowMultiplePerNode: true
  dashboard:
    enabled: true
  # cluster level storage configuration and selection
  storage:
    useAllNodes: false
    useAllDevices: false
    deviceFilter:
    location:
    config:
      databaseSizeMB: "1024"
      journalSizeMB: "1024"
    nodes:
    - name: "node1"
      location: rack=rack1   # a location can be specified for every node and will be added to the CRUSH map
      devices:
      - name: "sdb"
      - name: "sdc"
    - name: "node2"
      location: rack=rack2   # a location can be specified for every node and will be added to the CRUSH map
      devices:
      - name: "sdb"
      - name: "sdc"
    - name: "node3"
      location: rack=rack3   # a location can be specified for every node and will be added to the CRUSH map
      devices:
      - name: "sdb"
      - name: "sdc"

To utilize the location as a failureDomain, specify the corresponding option in your CephBlockPool

apiVersion: ceph.rook.io/v1
kind: CephBlockPool
metadata:
  name: replicapool
  namespace: rook-ceph
spec:
  failureDomain: rack        # this uses the location setting from the CephCluster
  replicated:
    size: 3

This configuration will split replication of your volumes across unique racks in your datacenter setup.