K8S 的 Volume[本地磁盘]
K8S 有很多 Volume 类型,详细信息可以查看官网https://kubernetes.io/docs/concepts/storage/volumes/#types-of-volumes;这里只介绍几种：emptyDir，local，hostPath
local
使 Volume 和 Pod 被分配到同一个 Node，实现数据的本地化，适合一些对读写磁盘数据要求比较高的，比如数据库
这种做法的风险是 Volume 和 Pod 都被绑定到固定的一个 Node （暂时不支持动态配置），一但这个 Node 出问题，会影响 Volume 和 Pod，可用性会降低
先创建一个 StorageClass
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer这里 WaitForFirstConsumer 表示不要立即绑定 Volume，而是等到 Pod 调度的时候再绑定
创建 PV
apiVersion: v1
kind: PersistentVolume
metadata:
name: tidb-pv
spec:
capacity:
storage: 10Gi
volumeMode: Filesystem
accessModes:
- ReadWriteMany
persistentVolumeReclaimPolicy: Delete
storageClassName: local-storage
local:
path: /mnt/disks
nodeAffinity:
required:
nodeSelectorTerms:
- matchExpressions:
- key: kubernetes.io/hostname
operator: In
values:
- k8s-node这个 PV 使用k8s-node 节点的 /mnt/disks 目录，并且指定 StorageClass 为前面创建的 local-storage
创建 PVC
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: tidb-pvc
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 5Gi
storageClassName: local-storage
通过指定 storageClass 为前面创建的 local-storage，这样会等到 Pod 调度的时候再绑定 PVC 和 PV，确保能找到合适的 PV 使得 Volume 和 Pod 在同一个 Node 上
创建 Pod
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: k8s.gcr.io/test-webserver
name: test-container
volumeMounts:
- mountPath: /cache
name: cache-volume
volumes:
- name: cache-volume
persistentVolumeClaim:
claimName: tidb-pvc
等这个 Pod 创建的时候 example-pvc 再去绑定合适的 pv 使得 Pod 和 Volume 跑在同一个 Node
local-volume-provisioner动态创建pv
local-volume-provisioner 程序是一个 DaemonSet，会在每个 Kubernetes 工作节点上启动一个 Pod,地址：https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner,首先下载 local-volume-provisioner.yaml 内容如下：
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: "local-storage"
provisioner: "kubernetes.io/no-provisioner"
volumeBindingMode: "WaitForFirstConsumer"
---
apiVersion: v1
kind: ConfigMap
metadata:
name: local-provisioner-config
namespace: kube-system
data:
setPVOwnerRef: "true"
nodeLabelsForPV: |
- kubernetes.io/hostname
storageClassMap: |
local-storage:
hostDir: /mnt/disks
mountDir: /mnt/disks
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: local-volume-provisioner
namespace: kube-system
labels:
app: local-volume-provisioner
spec:
selector:
matchLabels:
app: local-volume-provisioner
template:
metadata:
labels:
app: local-volume-provisioner
spec:
serviceAccountName: local-storage-admin
containers:
- image: "quay.io/external_storage/local-volume-provisioner:v2.3.4"
name: provisioner
securityContext:
privileged: true
env:
- name: MY_NODE_NAME
valueFrom:
fieldRef:
fieldPath: spec.nodeName
- name: MY_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
- name: JOB_CONTAINER_IMAGE
value: "quay.io/external_storage/local-volume-provisioner:v2.3.4"
resources:
requests:
cpu: 100m
memory: 100Mi
limits:
cpu: 100m
memory: 100Mi
volumeMounts:
- mountPath: /etc/provisioner/config
name: provisioner-config
readOnly: true
# mounting /dev in DinD environment would fail
# - mountPath: /dev
# name: provisioner-dev
- mountPath: /mnt/disks
name: local-disks
mountPropagation: "HostToContainer"
volumes:
- name: provisioner-config
configMap:
name: local-provisioner-config
# - name: provisioner-dev
# hostPath:
# path: /dev
- name: local-disks
hostPath:
path: /mnt/disks
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: local-storage-admin
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: local-storage-provisioner-pv-binding
namespace: kube-system
subjects:
- kind: ServiceAccount
name: local-storage-admin
namespace: kube-system
roleRef:
kind: ClusterRole
name: system:persistent-volume-provisioner
apiGroup: rbac.authorization.k8s.io
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: local-storage-provisioner-node-clusterrole
namespace: kube-system
rules:
- apiGroups: [""]
resources: ["nodes"]
verbs: ["get"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: local-storage-provisioner-node-binding
namespace: kube-system
subjects:
- kind: ServiceAccount
name: local-storage-admin
namespace: kube-system
roleRef:
kind: ClusterRole
name: local-storage-provisioner-node-clusterrole
apiGroup: rbac.authorization.k8s.io
挂载磁盘，其Provisioner本身其并不提供local volume，但它在各个节点上的provisioner会去动态的“发现”挂载点（discovery directory），当某node的provisioner在/mnt/disks目录下发现有挂载点时，会创建PV，该PV的local.path就是挂载点，并设置nodeAffinity为该node。lvp.sh
#!/bin/bash
for i in $(seq 1 5); do
mkdir -p /mnt/disks-bind/vol${i}
mkdir -p /mnt/disks/vol${i}
mount --bind /mnt/disks-bind/vol${i} /mnt/disks/vol${i}
done创建pvc
#创建挂在文件夹 每个节点都要执行
sh ./lvp.sh
#拉去镜像
docker pull quay.io/external_storage/local-volume-provisioner:v2.3.4
#docker save -o local-volume-provisioner-v2.3.4.tar quay.io/external_storage/local-volume-provisioner:v2.3.4
#docker load -i local-volume-provisioner-v2.3.4.tar
kubectl apply -f local-volume-provisioner.yaml
kubectl get po -n kube-system -l app=local-volume-provisioner && kubectl get pv | grep local-storage期望的结果：
root@k8s-master:~# kubectl get po -n kube-system -l app=local-volume-provisioner && kubectl get pv | grep local-storage
NAME READY STATUS RESTARTS AGE
local-volume-provisioner-wsvbf 1/1 Running 0 14m
local-volume-provisioner-xmn8t 1/1 Running 0 14m
local-pv-3a6d09fd 61Gi RWO Delete Available local-storage 2m45s
local-pv-53aadb5a 61Gi RWO Delete Available local-storage 2m45s
local-pv-68a5e781 61Gi RWO Delete Available local-storage 2m45s
local-pv-7077366c 61Gi RWO Delete Available local-storage 14m
local-pv-814f6123 61Gi RWO Delete Available local-storage 14m
local-pv-912b9c0a 61Gi RWO Delete Available local-storage 14m
local-pv-a361c37f 61Gi RWO Delete Available local-storage 14m
local-pv-af1f3de0 61Gi RWO Delete Available local-storage 2m45s
local-pv-e6354605 61Gi RWO Delete Available local-storage 14m
local-pv-ec4cb727 61Gi RWO Delete Available local-storage 2m45s
验证：pod.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: local-test
spec:
serviceName: "local-service"
replicas: 3
selector:
matchLabels:
app: local-test
template:
metadata:
labels:
app: local-test
spec:
containers:
- name: test-container
image: busybox
command:
- "/bin/sh"
args:
- "-c"
- "sleep 100000"
volumeMounts:
- name: local-vol
mountPath: /tmp
volumeClaimTemplates:
- metadata:
name: local-vol
spec:
accessModes: [ "ReadWriteOnce" ]
storageClassName: "local-storage"
resources:
requests:
storage: 2Gikubectl apply -f pod.yaml
emptyDir
初始化为空目录，只在 Pod 运行时存在，当 Pod 停止或死掉后，目录下的所有数据都会被删除（如果只是 Container 死掉数据不会被删除），可以被同一个 Pod 下的不同 Container 使用
emptyDir 主要用于某些应用程序无需永久保存的临时目录，在多个容器之间共享数据等场景
下面是一个简单的例子，将 emptyDir 的 volume 给 mount 到 /cache 目录
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: k8s.gcr.io/test-webserver
name: test-container
volumeMounts:
- mountPath: /cache
name: cache-volume
volumes:
- name: cache-volume
emptyDir: {}
缺省情况下，emptyDir 是在 Pod 运行的主机的文件系统上创建临时目录
此外也可以通过将 emptyDir.medium 设定为 "Memory" 从而使用内存作为文件系统，这种情况速度会比较快，但空间会比较小，而且如果主机重启数据会丢失
hostPath
把 Volume 挂到 host 主机的路径，这和 local 很像，但有区别
host 模式下 Pod 的运行节点是随机的，假设 Pod 第一次起来的时候是在 Node-A，这时会在 Node-A 创建目录挂到 Pod，如果后来 Pod crash 然后重启，可能会被分配到 Node-B，这时会在 Node-B 创建目录挂到 Pod，但是之前保存在 Node-A 的数据就丢失了
local 模式下 Pod 和创建的目录一直是在同一台主机上
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: k8s.gcr.io/test-webserver
name: test-container
volumeMounts:
- mountPath: /test-pd
name: test-volume
volumes:
- name: test-volume
hostPath:
# directory location on host
path: /data
# this field is optional
type: Directory
适用场景的例子，比如如果需要读取主机的系统路径 /sys，读取主机的 docker 信息 /var/lib/docker，这些都是固定路径，每台机都有，而且只关心本机的信息
参考：
https://www.cnblogs.com/moonlight-lin/p/13715817.html
https://docs.pingcap.com/zh/tidb-in-kubernetes/stable/configure-storage-class#%E6%9C%AC%E5%9C%B0-pv-%E9%85%8D%E7%BD%AE
https://www.jianshu.com/p/436945a25e9f