Alexander Trost
304eafa07d
Replace `rook-operator.yaml` mentions with `operator.yaml` as it is named right now. Signed-off-by: Alexander Trost <galexrt@googlemail.com>
149 lines
5.6 KiB
Markdown
149 lines
5.6 KiB
Markdown
---
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title: Shared File System
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weight: 26
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indent: true
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---
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# Shared File System
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A shared file system can be mounted with read/write permission from multiple pods. This may be useful for applications which can be clustered using a shared filesystem.
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This example runs a shared file system for the [kube-registry](https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/registry).
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### Prerequisites
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This guide assumes you have created a Rook cluster as explained in the main [Kubernetes guide](ceph-quickstart.md)
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### Multiple File Systems Not Supported
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By default only one shared file system can be created with Rook. Multiple file system support in Ceph is still considered experimental and can be enabled with the environment variable `ROOK_ALLOW_MULTIPLE_FILESYSTEMS` defined in `operator.yaml`.
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Please refer to [cephfs experimental features](http://docs.ceph.com/docs/master/cephfs/experimental-features/#multiple-filesystems-within-a-ceph-cluster) page for more information.
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## Create the File System
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Create the file system by specifying the desired settings for the metadata pool, data pools, and metadata server in the `Filesystem` CRD. In this example we create the metadata pool with replication of three and a single data pool with erasure coding. For more options, see the documentation on [creating shared file systems](ceph-filesystem-crd.md).
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Save this shared file system definition as `filesystem.yaml`:
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```yaml
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apiVersion: ceph.rook.io/v1beta1
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kind: Filesystem
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metadata:
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name: myfs
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namespace: rook-ceph
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spec:
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metadataPool:
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replicated:
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size: 3
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dataPools:
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- replicated:
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size: 3
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metadataServer:
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activeCount: 1
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activeStandby: true
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```
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The Rook operator will create all the pools and other resources necessary to start the service. This may take a minute to complete.
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```bash
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# Create the file system
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$ kubectl create -f filesystem.yaml
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# To confirm the file system is configured, wait for the mds pods to start
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$ kubectl -n rook-ceph get pod -l app=rook-ceph-mds
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NAME READY STATUS RESTARTS AGE
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rook-ceph-mds-myfs-7d59fdfcf4-h8kw9 1/1 Running 0 12s
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rook-ceph-mds-myfs-7d59fdfcf4-kgkjp 1/1 Running 0 12s
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```
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To see detailed status of the file system, start and connect to the [Rook toolbox](toolbox.md). A new line will be shown with `ceph status` for the `mds` service. In this example, there is one active instance of MDS which is up, with one MDS instance in `standby-replay` mode in case of failover.
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```bash
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$ ceph status
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...
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services:
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mds: myfs-1/1/1 up {[myfs:0]=mzw58b=up:active}, 1 up:standby-replay
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```
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## Consume the Shared File System: K8s Registry Sample
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As an example, we will start the kube-registry pod with the shared file system as the backing store.
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Save the following spec as `kube-registry.yaml`:
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```yaml
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apiVersion: v1
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kind: ReplicationController
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metadata:
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name: kube-registry-v0
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namespace: kube-system
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labels:
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k8s-app: kube-registry
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version: v0
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kubernetes.io/cluster-service: "true"
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spec:
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replicas: 3
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selector:
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k8s-app: kube-registry
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version: v0
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template:
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metadata:
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labels:
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k8s-app: kube-registry
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version: v0
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kubernetes.io/cluster-service: "true"
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spec:
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containers:
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- name: registry
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image: registry:2
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resources:
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limits:
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cpu: 100m
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memory: 100Mi
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env:
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- name: REGISTRY_HTTP_ADDR
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value: :5000
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- name: REGISTRY_STORAGE_FILESYSTEM_ROOTDIRECTORY
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value: /var/lib/registry
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volumeMounts:
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- name: image-store
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mountPath: /var/lib/registry
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ports:
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- containerPort: 5000
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name: registry
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protocol: TCP
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volumes:
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- name: image-store
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flexVolume:
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driver: ceph.rook.io/rook
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fsType: ceph
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options:
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fsName: myfs # name of the filesystem specified in the filesystem CRD.
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clusterNamespace: rook-ceph # namespace where the Rook cluster is deployed
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# by default the path is /, but you can override and mount a specific path of the filesystem by using the path attribute
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# the path must exist on the filesystem, otherwise mounting the filesystem at that path will fail
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# path: /some/path/inside/cephfs
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```
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After creating it with `kubectl create -f kube-registry.yaml`, you now have a docker registry which is HA with persistent storage.
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#### Kernel Version Requirement
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If the Rook cluster has more than one filesystem and the application pod is scheduled to a node with kernel version older than 4.7, inconsistent results may arise since kernels older than 4.7 do not support specifying filesystem namespaces.
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## Consume the Shared File System: Toolbox
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Once you have pushed an image to the registry (see the [instructions](https://github.com/kubernetes/kubernetes/tree/release-1.9/cluster/addons/registry) to expose and use the kube-registry), verify that kube-registry is using the filesystem that was configured above by mounting the shared file system in the toolbox pod. See the [Direct Filesystem](direct-tools.md#shared-filesystem-tools) topic for more details.
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## Teardown
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To clean up all the artifacts created by the file system demo:
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```bash
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kubectl delete -f kube-registry.yaml
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```
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To delete the filesystem components and backing data, delete the Filesystem CRD. **Warning: Data will be deleted**
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```
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kubectl -n rook-ceph delete Filesystem myfs
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```
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### Advanced Example: Erasure Coded Filesystem
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The Ceph filesystem example can be found here: [Ceph Shared File System - Samples - Erasure Coded](ceph-filesystem-crd.md#erasure-coded).
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