简介
openebs
openebs
openebs 有两类存储类型
Local Volumes
Replicated Volumes
Local Volumes 类型实现了自动分配 local-pv ，应用如果对存储 io 性能高的话，可能会考虑本地存储，那么local-pv 是一个比较好的选择，但是使用 local-pv 的话需要手动创建 pv、storageclass。openebs 就帮助我们实现了这一步，使得使用 local-pv 和使用分布式存储一样透明，简洁。
如何部署openebs
这里我们只使用 local-pv-hostpath ，即使用本地文件系统的存储，根据官网 介绍，不需要提前安装 iscsi
Helm 部署
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$ helm repo add openebs https://openebs.github.io/charts
$ helm repo update
$ helm install openebs --namespace openebs openebs/openebs --create-namespace
kubectl 部署
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kubectl apply -f https://openebs.github.io/charts/openebs-operator.yaml
安装成功后，默认会部署两个 storageclass ，我们目前需要 **openebs-hostpath。**默认存储目录为 ****/var/openebs/local
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$ kubectl get pods -n openebs
NAME READY STATUS RESTARTS AGE
openebs-localpv-provisioner-69c8648db7-cnj45 1/1 Running 0 33m
openebs-ndm-bbgpv 1/1 Running 0 33m
openebs-ndm-bxsbb 1/1 Running 0 33m
openebs-ndm-cluster-exporter-9d75d564d-qvqz6 1/1 Running 0 33m
openebs-ndm-kdg7b 1/1 Running 0 33m
openebs-ndm-node-exporter-9zm62 1/1 Running 0 33m
openebs-ndm-node-exporter-hlj7h 1/1 Running 0 33m
openebs-ndm-node-exporter-j6wj7 1/1 Running 0 33m
openebs-ndm-node-exporter-s5hk4 1/1 Running 0 33m
openebs-ndm-operator-789985cc47-r4hwj 1/1 Running 0 33m
openebs-ndm-qm4sw 1/1 Running 0 33m
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$ kubectl get sc
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
openebs-device openebs.io/local Delete WaitForFirstConsumer false 116s
openebs-hostpath openebs.io/local Delete WaitForFirstConsumer false 116s
如果需要更改的话，直接修改 openebs-operator.yaml，value 字段即可
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apiVersion : storage.k8s.io/v1
kind : StorageClass
metadata :
name : openebs-hostpath
annotations :
openebs.io/cas-type : local
cas.openebs.io/config : |
#hostpath type will create a PV by
# creating a sub-directory under the
# BASEPATH provided below.
- name : StorageType
value : "hostpath"
#Specify the location (directory) where
# where PV(volume) data will be saved.
# A sub-directory with pv-name will be
# created. When the volume is deleted,
# the PV sub-directory will be deleted.
#Default value is /var/openebs/local
- name : BasePath
value : "/var/openebs/local/"
验证
接下来我们创建一个 PVC 资源对象，Pods 使用这个 PVC 就可以从 OpenEBS 动态 Local PV Provisioner 中请求 Hostpath Local PV 了。
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# local-hostpath-pvc.yaml
apiVersion : v1
kind : PersistentVolumeClaim
metadata :
name : local-hostpath-pvc
spec :
storageClassName : openebs-hostpath
accessModes :
- ReadWriteOnce
resources :
requests :
storage : 5Gi
直接创建这个 PVC 即可：
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$ kubectl apply -f local-hostpath-pvc.yaml
$ kubectl get pvc local-hostpath-pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
local-hostpath-pvc Pending openebs-hostpath 12s
我们可以看到这个 PVC 的状态是 Pending，这是因为对应的 StorageClass 是延迟绑定模式，所以需要等到 Pod 消费这个 PVC 后才会去绑定，接下来我们去创建一个 Pod 来使用这个 PVC。
声明一个如下所示的 Pod 资源清单：
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# local-hostpath-pod.yaml
apiVersion : v1
kind : Pod
metadata :
name : hello-local-hostpath-pod
spec :
volumes :
- name : local-storage
persistentVolumeClaim :
claimName : local-hostpath-pvc
containers :
- name : hello-container
image : busybox
command :
- sh
- -c
- 'while true; do echo "`date` [`hostname`] Hello from OpenEBS Local PV." >> /mnt/store/greet.txt; sleep $(($RANDOM % 5 + 300)); done'
volumeMounts :
- mountPath : /mnt/store
name : local-storage
直接创建这个 Pod：
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$ kubectl apply - f local - hostpath - pod . yaml
$ kubectl get pods hello - local - hostpath - pod
NAME READY STATUS RESTARTS AGE
hello - local - hostpath - pod 1 / 1 Running 0 2 m7s
$ kubectl get pvc local - hostpath - pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
local - hostpath - pvc Bound pvc - 3f 4 a1a65 - 6 cbc - 42 bf - a1f8 - 87 ad238c0b88 5 Gi RWO openebs - hostpath 5 m41s
可以看到 Pod 运行成功后，PVC 也绑定上了一个自动生成的 PV，我们可以查看这个 PV 的详细信息：
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$ kubectl get pv pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88 -o yaml
apiVersion: v1
kind: PersistentVolume
metadata:
annotations:
pv.kubernetes.io/provisioned-by: openebs.io/local
creationTimestamp: "2021-01-07T02:48:14Z"
finalizers:
- kubernetes.io/pv-protection
labels:
openebs.io/cas-type: local-hostpath
......
name: pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88
resourceVersion: "21193802"
selfLink: /api/v1/persistentvolumes/pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88
uid: f7cccdb3-d23a-4831-86c3-4363eb1a8dee
spec:
accessModes:
- ReadWriteOnce
capacity:
storage: 5Gi
claimRef:
apiVersion: v1
kind: PersistentVolumeClaim
name: local-hostpath-pvc
namespace: default
resourceVersion: "21193645"
uid: 3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88
local:
fsType: ""
path: /var/openebs/local/pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88
nodeAffinity:
required:
nodeSelectorTerms:
- matchExpressions:
- key: kubernetes.io/hostname
operator: In
values:
- node2
persistentVolumeReclaimPolicy: Delete
storageClassName: openebs-hostpath
volumeMode: Filesystem
status:
phase: Bound
我们可以看到这个自动生成的 PV 和我们前面自己手动创建的 Local PV 基本上是一致的，和 node2 节点是亲和关系，本地数据目录位于 /var/openebs/local/pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88 下面
接着我们来验证下 volume 数据，前往 node2 节点查看下上面的数据目录中的数据：
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[ root@node2 ~] # ls /var/openebs/local/pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88
greet.txt
[ root@node2 ~] # cat /var/openebs/local/pvc-3f4a1a65-6cbc-42bf-a1f8-87ad238c0b88/greet.txt
Thu Jan 7 10:48:49 CST 2021 [ hello-local-hostpath-pod] Hello from OpenEBS Local PV.
Thu Jan 7 10:53:50 CST 2021 [ hello-local-hostpath-pod] Hello from OpenEBS Local PV.
可以看到 Pod 容器中的数据已经持久化到 Local PV 对应的目录中去了。但是需要注意的是 StorageClass 默认的数据回收策略是 Delete，所以如果将 PVC 删掉后数据会自动删除，我们可以 Velero 这样的工具来进行备份还原。
引用
openebs 官网
kubernetes 训练营
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