OpenEBS云原生存储使用
本文将指导您如何在Kubernetes集群上安装OpenEBS作为持久化存储。
我们将使用Operator的方式来安装OpenEBS，安装之前需要先确认您的节点上已经安装了iSCSI。
- 更多参考：
先决条件
OpenEBS依赖与iSCSI做存储管理，因此需要先确保您的集群上已有安装OpenEBS。
注意：如果您使用kubeadm，容器方式安装的kublet，那么其中会自带iSCSI，不需要再手动安装，如果是直接使用二进制形式在裸机上安装的kubelet，则需要自己安装iSCSI。
iSCSI( Internet Small Computer System Interface 互联网小型计算机系统接口)是一种基于TCP/IP 的协议，用来建立和管理IP存储设备、主机和客户机等之间的相互连接，并创建存储区域网络（SAN）。SAN 使得SCSI 协议应用于高速数据传输网络成为可能，这种传输以数据块级别（block-level）在多个数据存储网络间进行。SCSI 结构基于C/S模式，其通常应用环境是：设备互相靠近，并且这些设备由SCSI 总线连接。
OpenEBS需要使用iSCSI作为存储协议，而CentOS上默认是没有安装该软件的，因此我们需要手动安装。
iSCSI中包括两种类型的角色：
- target：用来提供存储（server）
- initiator：使用存储的客户端（client）
下图在Kubernetes中使用iSCSI的架构图（图片来源：http://rootfs.github.io/iSCSI-Kubernetes/）。
安装iSCSI服务十分简单，不需要额外的配置，只要安装后启动服务即可。
在每个node节点上执行下面的命令：
yum -y install iscsi-initiator-utils
systemctl enable iscsid
systemctl start iscsid
快速开始
使用Operator运行OpenEBS服务：
wget https://raw.githubusercontent.com/openebs/openebs/master/k8s/openebs-operator.yaml
kubectl apply -f openebs-operator.yaml
使用默认或自定义的storageclass：
wget https://raw.githubusercontent.com/openebs/openebs/master/k8s/openebs-storageclasses.yaml
kubectl apply -f openebs-storageclasses.yaml
用到的镜像有：
- openebs/m-apiserver:0.5.1-RC1
- openebs/openebs-k8s-provisioner:0.5.1-RC2
- openebs/jiva:0.5.1-RC1
- openebs/m-exporter:0.5.0
部署完的资源
(base) supermap@xriver02:~/openthings/openebs$ kubectl get all -n openebs
NAME READY STATUS RESTARTS AGE
pod/maya-apiserver-f9f7c6bb7-sm28z 1/1 Running 3 6m55s
pod/openebs-admission-server-7b9d59c456-9z924 1/1 Running 0 6m55s
pod/openebs-localpv-provisioner-6f67fb4868-ggfbd 1/1 Running 0 6m55s
pod/openebs-ndm-5sxrw 1/1 Running 0 6m55s
pod/openebs-ndm-ddpk2 1/1 Running 0 6m55s
pod/openebs-ndm-operator-67fbc66445-k8sbh 1/1 Running 0 6m55s
pod/openebs-ndm-x94mq 1/1 Running 0 6m55s
pod/openebs-provisioner-76cd669b6-pjlbf 1/1 Running 0 6m55s
pod/openebs-snapshot-operator-54d76b9-wxfhp 2/2 Running 0 6m55s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/admission-server-svc ClusterIP 10.104.243.49 <none> 443/TCP 5m44s
service/maya-apiserver-service ClusterIP 10.99.87.215 <none> 5656/TCP 6m55s
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE
daemonset.apps/openebs-ndm 3 3 3 3 3 <none> 6m55s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/maya-apiserver 1/1 1 1 6m55s
deployment.apps/openebs-admission-server 1/1 1 1 6m55s
deployment.apps/openebs-localpv-provisioner 1/1 1 1 6m55s
deployment.apps/openebs-ndm-operator 1/1 1 1 6m55s
deployment.apps/openebs-provisioner 1/1 1 1 6m55s
deployment.apps/openebs-snapshot-operator 1/1 1 1 6m55s
NAME DESIRED CURRENT READY AGE
replicaset.apps/maya-apiserver-f9f7c6bb7 1 1 1 6m55s
replicaset.apps/openebs-admission-server-7b9d59c456 1 1 1 6m55s
replicaset.apps/openebs-localpv-provisioner-6f67fb4868 1 1 1 6m55s
replicaset.apps/openebs-ndm-operator-67fbc66445 1 1 1 6m55s
replicaset.apps/openebs-provisioner-76cd669b6 1 1 1 6m55s
replicaset.apps/openebs-snapshot-operator-54d76b9 1 1 1 6m55s
测试
下面使用OpenEBS官方文档中的示例，安装Jenkins测试
wget https://raw.githubusercontent.com/openebs/openebs/master/k8s/demo/jenkins/jenkins.yml
kubectl apply -f jenkins.yml
查看PV和PVC
$ kubectl get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-8e203e86-f1e5-11e7-aa47-f4e9d49f8ed0 5G RWO Delete Bound default/jenkins-claim openebs-standard 1h
$ kubectl get pvc
kubectl get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
jenkins-claim Bound pvc-8e203e86-f1e5-11e7-aa47-f4e9d49f8ed0 5G RWO openebs-standard 1h
查看Jenkins pod：
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning FailedScheduling 29m (x2 over 29m) default-scheduler PersistentVolumeClaim is not bound: "jenkins-claim" (repeated 3 times)
Normal Scheduled 29m default-scheduler Successfully assigned jenkins-668dfbd847-vhg4c to 172.20.0.115
Normal SuccessfulMountVolume 29m kubelet, 172.20.0.115 MountVolume.SetUp succeeded for volume "default-token-3l9f0"
Warning FailedMount 27m kubelet, 172.20.0.115 Unable to mount volumes for pod "jenkins-668dfbd847-vhg4c_default(8e2ad467-f1e5-11e7-aa47-f4e9d49f8ed0)": timeout expired waiting for volumes to attach/mount for pod "default"/"jenkins-668dfbd847-vhg4c". list of unattached/unmounted volumes=[jenkins-home]
Warning FailedSync 27m kubelet, 172.20.0.115 Error syncing pod
Normal SuccessfulMountVolume 26m kubelet, 172.20.0.115 MountVolume.SetUp succeeded for volume "pvc-8e203e86-f1e5-11e7-aa47-f4e9d49f8ed0"
Normal Pulling 26m kubelet, 172.20.0.115 pulling image "sz-pg-oam-docker-hub-001.tendcloud.com/library/jenkins:lts"
Normal Pulled 26m kubelet, 172.20.0.115 Successfully pulled image "sz-pg-oam-docker-hub-001.tendcloud.com/library/jenkins:lts"
Normal Created 26m kubelet, 172.20.0.115 Created container
Normal Started 26m kubelet, 172.20.0.115 Started container
启动成功。Jenkins配置使用的是NodePort方式访问，现在访问集群中任何一个节点的Jenkins service的NodePort即可。
