121 lines
5.6 KiB
Markdown
121 lines
5.6 KiB
Markdown
# 使用OpenEBS做持久化存储
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本文将指导您如何在Kubernetes集群上安装[OpenEBS](https://github.com/openebs/openebs)作为持久化存储。
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我们将使用[Operator](https://coreos.com/operators/)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。
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## 先决条件
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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openiscsi。
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**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。
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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。
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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。
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iSCSI中包括两种类型的角色：
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- **target**：用来提供存储（server）
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- **initiator**：使用存储的客户端（client）
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下图在Kubernetes中使用iSCSI的架构图（图片来源：`http://rootfs.github.io/iSCSI-Kubernetes/`）。
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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。
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在每个node节点上执行下面的命令：
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```bash
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yum -y install iscsi-initiator-utils
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systemctl enable iscsid
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systemctl start iscsid
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```
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## 快速开始
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使用Operator运行OpenEBS服务：
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```bash
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wget https://raw.githubusercontent.com/openebs/openebs/master/k8s/openebs-operator.yaml
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kubectl apply -f openebs-operator.yaml
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```
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使用默认或自定义的storageclass：
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```bash
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wget https://raw.githubusercontent.com/openebs/openebs/master/k8s/openebs-storageclasses.yaml
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kubectl apply -f openebs-storageclasses.yaml
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```
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用到的镜像有：
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- openebs/m-apiserver:0.5.1-RC1
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- openebs/openebs-k8s-provisioner:0.5.1-RC2
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- openebs/jiva:0.5.1-RC1
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- openebs/m-exporter:0.5.0
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## 测试
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下面使用OpenEBS官方文档中的示例，安装Jenkins测试
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```bash
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wget https://raw.githubusercontent.com/openebs/openebs/master/k8s/demo/jenkins/jenkins.yml
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kubectl apply -f jenkins.yml
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```
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查看PV和PVC
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```bash
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$ kubectl get pv
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NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
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pvc-8e203e86-f1e5-11e7-aa47-f4e9d49f8ed0 5G RWO Delete Bound default/jenkins-claim openebs-standard 1h
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$ kubectl get pvc
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kubectl get pvc
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NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
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jenkins-claim Bound pvc-8e203e86-f1e5-11e7-aa47-f4e9d49f8ed0 5G RWO openebs-standard 1h
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```
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查看Jenkins pod
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```bash
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Warning FailedScheduling 29m (x2 over 29m) default-scheduler PersistentVolumeClaim is not bound: "jenkins-claim" (repeated 3 times)
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Normal Scheduled 29m default-scheduler Successfully assigned jenkins-668dfbd847-vhg4c to 172.20.0.115
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Normal SuccessfulMountVolume 29m kubelet, 172.20.0.115 MountVolume.SetUp succeeded for volume "default-token-3l9f0"
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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]
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Warning FailedSync 27m kubelet, 172.20.0.115 Error syncing pod
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Normal SuccessfulMountVolume 26m kubelet, 172.20.0.115 MountVolume.SetUp succeeded for volume "pvc-8e203e86-f1e5-11e7-aa47-f4e9d49f8ed0"
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Normal Pulling 26m kubelet, 172.20.0.115 pulling image "harbor-001.jimmysong.io/library/jenkins:lts"
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Normal Pulled 26m kubelet, 172.20.0.115 Successfully pulled image "harbor-001.jimmysong.io/library/jenkins:lts"
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Normal Created 26m kubelet, 172.20.0.115 Created container
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Normal Started 26m kubelet, 172.20.0.115 Started container
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```
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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。
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## 存储策略
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OpenEBS的存储策略使用StorageClaass实现，包括如下的StorageClass：
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- openebs-cassandra
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- openebs-es-data-sc
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- openebs-jupyter
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- openebs-kafka
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- openebs-mongodb
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- openebs-percona
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- openebs-redis
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- openebs-standalone
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- openebs-standard
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- openebs-zk
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## 参考
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- [CentOS 7.x 下配置iSCSI网络存储](http://blog.csdn.net/wh211212/article/details/52981305)
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- [Configure iSCSI Initiator](https://www.server-world.info/en/note?os=CentOS_7&p=iscsi&f=2)
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- [RHEL7: Configure a system as either an iSCSI target or initiator that persistently mounts an iSCSI target.](https://www.certdepot.net/rhel7-configure-iscsi-target-initiator-persistently/)
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