ceph/doc/rbd/rbd-kubernetes.rst
Kefu Chai 0cb56e0f13 doc: use plantweb as fallback of sphinx-ditaa
RTD does not support installing system packages, the only ways to install
dependencies are setuptools and pip. while ditaa is a tool written in
Java. so we need to find a native python tool allowing us to render ditaa
images. plantweb is able to the web service for rendering the ditaa
diagram. so let's use it as a fallback if "ditaa" is not around.

also start a new line after the directive, otherwise planweb server will
return 500 at seeing the diagram.

Signed-off-by: Kefu Chai <kchai@redhat.com>
2020-04-10 08:38:06 +08:00

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==============================
Block Devices and Kubernetes
==============================
You may use Ceph Block Device images with Kubernetes v1.13 and later through
`ceph-csi`_, which dynamically provisions RBD images to back Kubernetes
`volumes`_ and maps these RBD images as block devices (optionally mounting
a file system contained within the image) on worker nodes running
`pods`_ that reference an RBD-backed volume. Ceph stripes block device images as
objects across the cluster, which means that large Ceph Block Device images have
better performance than a standalone server!
To use Ceph Block Devices with Kubernetes v1.13 and higher, you must install
and configure ``ceph-csi`` within your Kubernetes environment. The following
diagram depicts the Kubernetes/Ceph technology stack.
.. ditaa::
+---------------------------------------------------+
| Kubernetes |
+---------------------------------------------------+
| ceph--csi |
+------------------------+--------------------------+
|
| configures
v
+------------------------+ +------------------------+
| | | rbd--nbd |
| Kernel Modules | +------------------------+
| | | librbd |
+------------------------+-+------------------------+
| RADOS Protocol |
+------------------------+-+------------------------+
| OSDs | | Monitors |
+------------------------+ +------------------------+
.. important::
``ceph-csi`` uses the RBD kernel modules by default which may not support all
Ceph `CRUSH tunables`_ or `RBD image features`_.
Create a Pool
=============
By default, Ceph block devices use the ``rbd`` pool. Create a pool for
Kubernetes volume storage. Ensure your Ceph cluster is running, then create
the pool. ::
$ ceph osd pool create kubernetes
See `Create a Pool`_ for details on specifying the number of placement groups
for your pools, and `Placement Groups`_ for details on the number of placement
groups you should set for your pools.
A newly created pool must be initialized prior to use. Use the ``rbd`` tool
to initialize the pool::
$ rbd pool init kubernetes
Configure ceph-csi
==================
Setup Ceph Client Authentication
--------------------------------
Create a new user for Kubernetes and `ceph-csi`. Execute the following and
record the generated key::
$ ceph auth get-or-create client.kubernetes mon 'profile rbd' osd 'profile rbd pool=kubernetes' mgr 'profile rbd pool=kubernetes'
[client.kubernetes]
key = AQD9o0Fd6hQRChAAt7fMaSZXduT3NWEqylNpmg==
Generate `ceph-csi` `ConfigMap`
-------------------------------
The `ceph-csi` requires a `ConfigMap` object stored in Kubernetes to define the
the Ceph monitor addresses for the Ceph cluster. Collect both the Ceph cluster
unique `fsid` and the monitor addresses::
$ ceph mon dump
<...>
fsid b9127830-b0cc-4e34-aa47-9d1a2e9949a8
<...>
0: [v2:192.168.1.1:3300/0,v1:192.168.1.1:6789/0] mon.a
1: [v2:192.168.1.2:3300/0,v1:192.168.1.2:6789/0] mon.b
2: [v2:192.168.1.3:3300/0,v1:192.168.1.3:6789/0] mon.c
.. note::
``ceph-csi`` currently only supports the `legacy V1 protocol`_.
Generate a `csi-config-map.yaml` file similar to the example below, substituting
the `fsid` for "clusterID", and the monitor addresses for "monitors"::
$ cat <<EOF > csi-config-map.yaml
---
apiVersion: v1
kind: ConfigMap
data:
config.json: |-
[
{
"clusterID": "b9127830-b0cc-4e34-aa47-9d1a2e9949a8",
"monitors": [
"192.168.1.1:6789",
"192.168.1.2:6789",
"192.168.1.3:6789"
]
}
]
metadata:
name: ceph-csi-config
EOF
Once generated, store the new `ConfigMap` object in Kubernetes::
$ kubectl apply -f csi-config-map.yaml
Generate `ceph-csi` cephx `Secret`
----------------------------------
`ceph-csi` requires the cephx credentials for communicating with the Ceph
cluster. Generate a `csi-rbd-secret.yaml` file similar to the example below,
using the newly created Kubernetes user id and cephx key::
$ cat <<EOF > csi-rbd-secret.yaml
---
apiVersion: v1
kind: Secret
metadata:
name: csi-rbd-secret
namespace: default
stringData:
userID: kubernetes
userKey: AQD9o0Fd6hQRChAAt7fMaSZXduT3NWEqylNpmg==
EOF
Once generated, store the new `Secret` object in Kubernetes::
$ kubectl apply -f csi-rbd-secret.yaml
Configure `ceph-csi` Plugins
----------------------------
Create the required `ServiceAccount` and RBAC `ClusterRole`/`ClusterRoleBinding`
Kubernetes objects. These objects do not necessarily need to be customized for
your Kubernetes environment and therefore can be used as-is from the `ceph-csi`
deployment YAMLs::
$ kubectl apply -f https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-provisioner-rbac.yaml
$ kubectl apply -f https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-nodeplugin-rbac.yaml
Finally, create the `ceph-csi` provisioner and node plugins. With the
possible exception of the `ceph-csi` container release version, these objects do
not necessarily need to be customized for your Kubernetes environment and
therefore can be used as-is from the `ceph-csi` deployment YAMLs::
$ wget https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-rbdplugin-provisioner.yaml
$ kubectl apply -f csi-rbdplugin-provisioner.yaml
$ wget https://raw.githubusercontent.com/ceph/ceph-csi/master/deploy/rbd/kubernetes/csi-rbdplugin.yaml
$ kubectl apply -f csi-rbdplugin.yaml
.. important::
The provisioner and node plugin YAMLs will, by default, pull the development
release of the `ceph-csi` container (quay.io/cephcsi/cephcsi:canary).
The YAMLs should be updated to use a release version container for
production workloads.
Using Ceph Block Devices
========================
Create a `StorageClass`
-----------------------
The Kubernetes `StorageClass` defines a class of storage. Multiple `StorageClass`
objects can be created to map to different quality-of-service levels (i.e. NVMe
vs HDD-based pools) and features.
For example, to create a `ceph-csi` `StorageClass` that maps to the `kubernetes`
pool created above, the following YAML file can be used after ensuring that the
"clusterID" property matches your Ceph cluster's `fsid`::
$ cat <<EOF > csi-rbd-sc.yaml
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: csi-rbd-sc
provisioner: rbd.csi.ceph.com
parameters:
clusterID: b9127830-b0cc-4e34-aa47-9d1a2e9949a8
pool: kubernetes
csi.storage.k8s.io/provisioner-secret-name: csi-rbd-secret
csi.storage.k8s.io/provisioner-secret-namespace: default
csi.storage.k8s.io/node-stage-secret-name: csi-rbd-secret
csi.storage.k8s.io/node-stage-secret-namespace: default
reclaimPolicy: Delete
mountOptions:
- discard
EOF
$ kubectl apply -f csi-rbd-sc.yaml
Create a `PersistentVolumeClaim`
--------------------------------
A `PersistentVolumeClaim` is a request for abstract storage resources by a user.
The `PersistentVolumeClaim` would then be associated to a `Pod` resource to
provision a `PersistentVolume`, which would be backed by a Ceph block image.
An optional `volumeMode` can be included to select between a mounted file system
(default) or raw block device-based volume.
Using `ceph-csi`, specifying `Filesystem` for `volumeMode` can support both
`ReadWriteOnce` and `ReadOnlyMany` `accessMode` claims, and specifying `Block`
for `volumeMode` can support `ReadWriteOnce`, `ReadWriteMany`, and
`ReadOnlyMany` `accessMode` claims.
For example, to create a block-based `PersistentVolumeClaim` that utilizes
the `ceph-csi`-based `StorageClass` created above, the following YAML can be
used to request raw block storage from the `csi-rbd-sc` `StorageClass`::
$ cat <<EOF > raw-block-pvc.yaml
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: raw-block-pvc
spec:
accessModes:
- ReadWriteOnce
volumeMode: Block
resources:
requests:
storage: 1Gi
storageClassName: csi-rbd-sc
EOF
$ kubectl apply -f raw-block-pvc.yaml
The following demonstrates and example of binding the above
`PersistentVolumeClaim` to a `Pod` resource as a raw block device::
$ cat <<EOF > raw-block-pod.yaml
---
apiVersion: v1
kind: Pod
metadata:
name: pod-with-raw-block-volume
spec:
containers:
- name: fc-container
image: fedora:26
command: ["/bin/sh", "-c"]
args: ["tail -f /dev/null"]
volumeDevices:
- name: data
devicePath: /dev/xvda
volumes:
- name: data
persistentVolumeClaim:
claimName: raw-block-pvc
EOF
$ kubectl apply -f raw-block-pod.yaml
To create a file-system-based `PersistentVolumeClaim` that utilizes the
`ceph-csi`-based `StorageClass` created above, the following YAML can be used to
request a mounted file system (backed by an RBD image) from the `csi-rbd-sc`
`StorageClass`::
$ cat <<EOF > pvc.yaml
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: rbd-pvc
spec:
accessModes:
- ReadWriteOnce
volumeMode: Filesystem
resources:
requests:
storage: 1Gi
storageClassName: csi-rbd-sc
EOF
$ kubectl apply -f pvc.yaml
The following demonstrates and example of binding the above
`PersistentVolumeClaim` to a `Pod` resource as a mounted file system::
$ cat <<EOF > pod.yaml
---
apiVersion: v1
kind: Pod
metadata:
name: csi-rbd-demo-pod
spec:
containers:
- name: web-server
image: nginx
volumeMounts:
- name: mypvc
mountPath: /var/lib/www/html
volumes:
- name: mypvc
persistentVolumeClaim:
claimName: rbd-pvc
readOnly: false
EOF
$ kubectl apply -f pod.yaml
.. _ceph-csi: https://github.com/ceph/ceph-csi/
.. _volumes: https://kubernetes.io/docs/concepts/storage/volumes/
.. _pods: https://kubernetes.io/docs/concepts/workloads/pods/pod-overview/
.. _Create a Pool: ../../rados/operations/pools#createpool
.. _Placement Groups: ../../rados/operations/placement-groups
.. _CRUSH tunables: ../../rados/operations/crush-map/#tunables
.. _RBD image features: ../rbd-config-ref/#image-features
.. _legacy V1 protocol: ../../rados/configuration/msgr2/#address-formats