Centos7下使用Ceph-deploy快速部署Ceph分布式存储-操作记录

时间:2021-08-10 12:54:57

 

之前已详细介绍了Ceph分布式存储基础知识,下面简单记录下Centos7使用Ceph-deploy快速部署Ceph环境:
1)基本环境

192.168.10.220    ceph-admin(ceph-deploy)   mds1、mon1(也可以将monit节点另放一台机器)
192.168.10.239    ceph-node1                  osd1   
192.168.10.212    ceph-node2                  osd2  
192.168.10.213    ceph-node3                  osd3   
-------------------------------------------------
每个节点修改修改主机名
# hostnamectl set-hostname ceph-admin
# hostnamectl set-hostname ceph-node1
# hostnamectl set-hostname ceph-node2
# hostnamectl set-hostname ceph-node3
-------------------------------------------------
每个节点修改配置文件
# cat /etc/hosts
192.168.10.220    ceph-admin
192.168.10.239    ceph-node1  
192.168.10.212    ceph-node2 
192.168.10.213    ceph-node3
-------------------------------------------------
每个节点确认连通性
# ping -c 3 ceph-admin
# ping -c 3 ceph-node1
# ping -c 3 ceph-node2
# ping -c 3 ceph-node3
-------------------------------------------------
每个节点关闭防火墙和selinux
# systemctl stop firewalld
# systemctl disable firewalld
# sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config
# setenforce 0
-------------------------------------------------
每个节点安装和配置NTP(官方推荐的是集群的所有节点全部安装并配置 NTP,需要保证各节点的系统时间一致。没有自己部署ntp服务器,就在线同步NTP)
# yum install ntp ntpdate ntp-doc -y
# systemctl restart ntpd
# systemctl status ntpd
-------------------------------------------------
每个节点准备yum源
删除默认的源,国外的比较慢
# yum clean all
# mkdir /mnt/bak
# mv /etc/yum.repos.d/* /mnt/bak/

下载阿里云的base源和epel源
# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
# wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo

添加ceph源
# vim /etc/yum.repos.d/ceph.repo
[ceph]
name=ceph
baseurl=http://mirrors.aliyun.com/ceph/rpm-jewel/el7/x86_64/
gpgcheck=0
priority =1
[ceph-noarch]
name=cephnoarch
baseurl=http://mirrors.aliyun.com/ceph/rpm-jewel/el7/noarch/
gpgcheck=0
priority =1
[ceph-source]
name=Ceph source packages
baseurl=http://mirrors.aliyun.com/ceph/rpm-jewel/el7/SRPMS
gpgcheck=0
priority=1
------------------------------------------------------------
每个节点创建cephuser用户,设置sudo权限
# useradd -d /home/cephuser -m cephuser
# echo "cephuser"|passwd --stdin cephuser
# echo "cephuser ALL = (root) NOPASSWD:ALL" | sudo tee /etc/sudoers.d/cephuser
# chmod 0440 /etc/sudoers.d/cephuser
# sed -i s'/Defaults requiretty/#Defaults requiretty'/g /etc/sudoers

测试cephuser的sudo权限
# su - cephuser
$ sudo su -
# 
------------------------------------------------------------
配置相互间的ssh信任关系
现在ceph-admin节点上产生公私钥文件,然后将ceph-admin节点的.ssh目录拷贝给其他节点
[root@ceph-admin ~]# su - cephuser
[cephuser@ceph-admin ~]$ ssh-keygen -t rsa    #一路回车
[cephuser@ceph-admin ~]$ cd .ssh/
[cephuser@ceph-admin .ssh]$ ls
id_rsa  id_rsa.pub
[cephuser@ceph-admin .ssh]$ cp id_rsa.pub authorized_keys

[cephuser@ceph-admin .ssh]$ scp -r /home/cephuser/.ssh ceph-node1:/home/cephuser/
[cephuser@ceph-admin .ssh]$ scp -r /home/cephuser/.ssh ceph-node2:/home/cephuser/
[cephuser@ceph-admin .ssh]$ scp -r /home/cephuser/.ssh ceph-node3:/home/cephuser/

然后在各节点直接验证cephuser用户下的ssh相互信任关系
$ ssh -p22 cephuser@ceph-admin
$ ssh -p22 cephuser@ceph-node1
$ ssh -p22 cephuser@ceph-node2
$ ssh -p22 cephuser@ceph-node3

2)准备磁盘(ceph-node1、ceph-node2、ceph-node3三个节点)

测试时使用的磁盘不要太小,否则后面添加磁盘时会报错,建议磁盘大小为20G及以上。
三个节点均是在WebvirtMgr上创建的虚拟机,参考:https://www.cnblogs.com/kevingrace/p/8387999.html 文档中创建并挂载虚拟机磁盘。
如下分别在三个节点挂载了一块20G的裸盘

检查磁盘
$ sudo fdisk -l /dev/vdb
Disk /dev/vdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

格式化磁盘
$ sudo parted -s /dev/vdb mklabel gpt mkpart primary xfs 0% 100%
$ sudo mkfs.xfs /dev/vdb -f

查看磁盘格式(xfs格式)
$ sudo blkid -o value -s TYPE /dev/vdb

3)部署阶段(ceph-admin节点上使用ceph-deploy快速部署)

[root@ceph-admin ~]# su - cephuser
   
安装ceph-deploy
[cephuser@ceph-admin ~]$ sudo yum update -y && sudo yum install ceph-deploy -y
   
创建cluster目录
[cephuser@ceph-admin ~]$ mkdir cluster
[cephuser@ceph-admin ~]$ cd cluster/
   
创建集群(后面填写monit节点的主机名,这里monit节点和管理节点是同一台机器,即ceph-admin)
[cephuser@ceph-admin cluster]$ ceph-deploy new ceph-admin
.........
[ceph-admin][DEBUG ] IP addresses found: [u'192.168.10.220']
[ceph_deploy.new][DEBUG ] Resolving host ceph-admin
[ceph_deploy.new][DEBUG ] Monitor ceph-admin at 192.168.10.220
[ceph_deploy.new][DEBUG ] Monitor initial members are ['ceph-admin']
[ceph_deploy.new][DEBUG ] Monitor addrs are ['192.168.10.220']
[ceph_deploy.new][DEBUG ] Creating a random mon key...
[ceph_deploy.new][DEBUG ] Writing monitor keyring to ceph.mon.keyring...
[ceph_deploy.new][DEBUG ] Writing initial config to ceph.conf...
   
修改ceph.conf文件(注意:mon_host必须和public network 网络是同网段内!)
[cephuser@ceph-admin cluster]$ vim ceph.conf     #添加下面两行配置内容
......
public network = 192.168.10.220/24
osd pool default size = 3
   
安装ceph(过程有点长,需要等待一段时间....)
[cephuser@ceph-admin cluster]$ ceph-deploy install ceph-admin ceph-node1 ceph-node2 ceph-node3
   
初始化monit监控节点,并收集所有密钥
[cephuser@ceph-admin cluster]$ ceph-deploy mon create-initial
[cephuser@ceph-admin cluster]$ ceph-deploy gatherkeys ceph-admin
   
添加OSD到集群
检查OSD节点上所有可用的磁盘
[cephuser@ceph-admin cluster]$ ceph-deploy disk list ceph-node1 ceph-node2 ceph-node3
   
使用zap选项删除所有osd节点上的分区
[cephuser@ceph-admin cluster]$ ceph-deploy disk zap ceph-node1:/dev/vdb ceph-node2:/dev/vdb ceph-node3:/dev/vdb
   
准备OSD(使用prepare命令)
[cephuser@ceph-admin cluster]$ ceph-deploy osd prepare ceph-node1:/dev/vdb ceph-node2:/dev/vdb ceph-node3:/dev/vdb
   
激活OSD(注意由于ceph对磁盘进行了分区,/dev/vdb磁盘分区为/dev/vdb1)
[cephuser@ceph-admin cluster]$ ceph-deploy osd activate ceph-node1:/dev/vdb1 ceph-node2:/dev/vdb1 ceph-node3:/dev/vdb1
---------------------------------------------------------------------------------------------
可能出现下面的报错:
[ceph-node1][WARNIN] ceph_disk.main.Error: Error: /dev/vdb1 is not a directory or block device
[ceph-node1][ERROR ] RuntimeError: command returned non-zero exit status: 1
[ceph_deploy][ERROR ] RuntimeError: Failed to execute command: /usr/sbin/ceph-disk -v activate --mark-init systemd --mount /dev/vdb1
   
但是这个报错没有影响ceph的部署,在三个osd节点上通过命令已显示磁盘已成功mount:
[cephuser@ceph-node1 ~]$ lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0              11:0    1  4.2G  0 rom
vda             252:0    0   70G  0 disk
├─vda1          252:1    0    1G  0 part /boot
└─vda2          252:2    0   69G  0 part
  ├─centos-root 253:0    0 43.8G  0 lvm  /
  ├─centos-swap 253:1    0  3.9G  0 lvm  [SWAP]
  └─centos-home 253:2    0 21.4G  0 lvm  /home
vdb             252:16   0   20G  0 disk
├─vdb1          252:17   0   15G  0 part /var/lib/ceph/osd/ceph-0       #挂载成功
└─vdb2          252:18   0    5G  0 part
  
[cephuser@ceph-node2 ~]$ lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0              11:0    1  4.2G  0 rom
vda             252:0    0   70G  0 disk
├─vda1          252:1    0    1G  0 part /boot
└─vda2          252:2    0   69G  0 part
  ├─centos-root 253:0    0 43.8G  0 lvm  /
  ├─centos-swap 253:1    0  3.9G  0 lvm  [SWAP]
  └─centos-home 253:2    0 21.4G  0 lvm  /home
vdb             252:16   0   20G  0 disk
├─vdb1          252:17   0   15G  0 part /var/lib/ceph/osd/ceph-1        #挂载成功
└─vdb2          252:18   0    5G  0 part
  
[cephuser@ceph-node3 ~]$ lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0              11:0    1  4.2G  0 rom
vda             252:0    0   70G  0 disk
├─vda1          252:1    0    1G  0 part /boot
└─vda2          252:2    0   69G  0 part
  ├─centos-root 253:0    0 43.8G  0 lvm  /
  ├─centos-swap 253:1    0  3.9G  0 lvm  [SWAP]
  └─centos-home 253:2    0 21.4G  0 lvm  /home
vdb             252:16   0   20G  0 disk
├─vdb1          252:17   0   15G  0 part /var/lib/ceph/osd/ceph-2       #挂载成功
└─vdb2          252:18   0    5G  0 part
  
查看OSD
[cephuser@ceph-admin cluster]$ ceph-deploy disk list ceph-node1 ceph-node2 ceph-node3
........
[ceph-node1][DEBUG ]  /dev/vdb2 ceph journal, for /dev/vdb1      #如下显示这两个分区,则表示成功了
[ceph-node1][DEBUG ]  /dev/vdb1 ceph data, active, cluster ceph, osd.0, journal /dev/vdb2
........
[ceph-node3][DEBUG ]  /dev/vdb2 ceph journal, for /dev/vdb1          
[ceph-node3][DEBUG ]  /dev/vdb1 ceph data, active, cluster ceph, osd.1, journal /dev/vdb2
.......
[ceph-node3][DEBUG ]  /dev/vdb2 ceph journal, for /dev/vdb1
[ceph-node3][DEBUG ]  /dev/vdb1 ceph data, active, cluster ceph, osd.2, journal /dev/vdb2
  
  
用ceph-deploy把配置文件和admin密钥拷贝到管理节点和Ceph节点,这样你每次执行Ceph命令行时就无需指定monit节点地址
和ceph.client.admin.keyring了
[cephuser@ceph-admin cluster]$ ceph-deploy admin ceph-admin ceph-node1 ceph-node2 ceph-node3
  
修改密钥权限
[cephuser@ceph-admin cluster]$ sudo chmod 644 /etc/ceph/ceph.client.admin.keyring
  
检查ceph状态
[cephuser@ceph-admin cluster]$ sudo ceph health
HEALTH_OK
[cephuser@ceph-admin cluster]$ sudo ceph -s
    cluster 33bfa421-8a3b-40fa-9f14-791efca9eb96
     health HEALTH_OK
     monmap e1: 1 mons at {ceph-admin=192.168.10.220:6789/0}
            election epoch 3, quorum 0 ceph-admin
     osdmap e14: 3 osds: 3 up, 3 in
            flags sortbitwise,require_jewel_osds
      pgmap v29: 64 pgs, 1 pools, 0 bytes data, 0 objects
            100 MB used, 45946 MB / 46046 MB avail
                  64 active+clean
 
查看ceph osd运行状态
[cephuser@ceph-admin ~]$ ceph osd stat
     osdmap e19: 3 osds: 3 up, 3 in
            flags sortbitwise,require_jewel_osds

查看osd的目录树
[cephuser@ceph-admin ~]$ ceph osd tree
ID WEIGHT  TYPE NAME           UP/DOWN REWEIGHT PRIMARY-AFFINITY 
-1 0.04376 root default                                          
-2 0.01459     host ceph-node1                                   
 0 0.01459         osd.0            up  1.00000          1.00000 
-3 0.01459     host ceph-node2                                   
 1 0.01459         osd.1            up  1.00000          1.00000 
-4 0.01459     host ceph-node3                                   
 2 0.01459         osd.2            up  1.00000          1.00000 

查看monit监控节点的服务情况
[root@ceph-admin ~]# ps -ef|grep cluster
ceph     28190     1  0 11:44 ?        00:00:01 /usr/bin/ceph-mon -f --cluster ceph --id ceph-admin --setuser ceph --setgroup ceph
 
分别查看下ceph-node1、ceph-node2、ceph-node3三个节点的osd服务情况,发现已经在启动中。
[cephuser@ceph-node1 ~]$ sudo ps -ef|grep ceph|grep "cluster"
ceph     28749     1  0 11:44 ?        00:00:00 /usr/bin/ceph-osd -f --cluster ceph --id 0 --setuser ceph --setgroup ceph
cephuser 29197 29051  0 11:54 pts/2    00:00:00 grep --color=auto cluster
  
[cephuser@ceph-node2 ~]$ sudo ps -ef|grep ceph|grep "cluster"
ceph     28749     1  0 11:44 ?        00:00:00 /usr/bin/ceph-osd -f --cluster ceph --id 0 --setuser ceph --setgroup ceph
cephuser 29197 29051  0 11:54 pts/2    00:00:00 grep --color=auto cluster
  
[cephuser@ceph-node3 ~]$ sudo ps -ef|grep ceph|grep "cluster"
ceph     28749     1  0 11:44 ?        00:00:00 /usr/bin/ceph-osd -f --cluster ceph --id 0 --setuser ceph --setgroup ceph
cephuser 29197 29051  0 11:54 pts/2    00:00:00 grep --color=auto cluster

==========================清除ceph存储======================

清除安装包
[cephuser@ceph-admin ~]$ ceph-deploy purge ceph1 ceph2 ceph3

清除配置信息
[cephuser@ceph-admin ~]$ ceph-deploy purgedata ceph1 ceph2 ceph3
[cephuser@ceph-admin ~]$ ceph-deploy forgetkeys

每个节点删除残留的配置文件
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/osd/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/mon/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/mds/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/bootstrap-mds/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/bootstrap-osd/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/bootstrap-mon/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/lib/ceph/tmp/*
[cephuser@ceph-admin ~]$ sudo rm -rf /etc/ceph/*
[cephuser@ceph-admin ~]$ sudo rm -rf /var/run/ceph/*

4)创建文件系统

先查看管理节点状态,默认是没有管理节点的。
[cephuser@ceph-admin ~]$ ceph mds stat
e1:

创建管理节点(ceph-admin作为管理节点)。
需要注意:如果不创建mds管理节点,client客户端将不能正常挂载到ceph集群!!
[cephuser@ceph-admin ~]$ pwd
/home/cephuser
[cephuser@ceph-admin ~]$ cd cluster/
[cephuser@ceph-admin cluster]$ ceph-deploy mds create ceph-admin

再次查看管理节点状态,发现已经在启动中
[cephuser@ceph-admin cluster]$ ceph mds stat
e2:, 1 up:standby
[root@ceph-admin ~]# ps -ef|grep cluster|grep ceph-mds
ceph     29093     1  0 12:46 ?        00:00:00 /usr/bin/ceph-mds -f --cluster ceph --id ceph-admin --setuser ceph --setgroup ceph

创建pool,pool是ceph存储数据时的逻辑分区,它起到namespace的作用
[cephuser@ceph-admin cluster]$ ceph osd lspools           #先查看pool
0 rbd,

新创建的ceph集群只有rdb一个pool。这时需要创建一个新的pool
[cephuser@ceph-admin cluster]$ ceph osd pool create cephfs_data 10       #后面的数字是PG的数量
pool 'cephfs_data' created

[cephuser@ceph-admin cluster]$ ceph osd pool create cephfs_metadata 10     #创建pool的元数据
pool 'cephfs_metadata' created

[cephuser@ceph-admin cluster]$ ceph fs new myceph cephfs_metadata cephfs_data
new fs with metadata pool 2 and data pool 1

再次查看pool状态
[cephuser@ceph-admin cluster]$ ceph osd lspools
0 rbd,1 cephfs_data,2 cephfs_metadata,

检查mds管理节点状态
[cephuser@ceph-admin cluster]$ ceph mds stat
e5: 1/1/1 up {0=ceph-admin=up:active}

查看ceph集群状态
[cephuser@ceph-admin cluster]$ sudo ceph -s
    cluster 33bfa421-8a3b-40fa-9f14-791efca9eb96
     health HEALTH_OK
     monmap e1: 1 mons at {ceph-admin=192.168.10.220:6789/0}
            election epoch 3, quorum 0 ceph-admin
      fsmap e5: 1/1/1 up {0=ceph-admin=up:active}           #多了此行状态
     osdmap e19: 3 osds: 3 up, 3 in
            flags sortbitwise,require_jewel_osds
      pgmap v48: 84 pgs, 3 pools, 2068 bytes data, 20 objects
            101 MB used, 45945 MB / 46046 MB avail
                  84 active+clean

查看ceph集群端口
[cephuser@ceph-admin cluster]$ sudo lsof -i:6789
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
ceph-mon 28190 ceph   10u  IPv4  70217      0t0  TCP ceph-admin:smc-https (LISTEN)
ceph-mon 28190 ceph   19u  IPv4  70537      0t0  TCP ceph-admin:smc-https->ceph-node1:41308 (ESTABLISHED)
ceph-mon 28190 ceph   20u  IPv4  70560      0t0  TCP ceph-admin:smc-https->ceph-node2:48516 (ESTABLISHED)
ceph-mon 28190 ceph   21u  IPv4  70583      0t0  TCP ceph-admin:smc-https->ceph-node3:44948 (ESTABLISHED)
ceph-mon 28190 ceph   22u  IPv4  72643      0t0  TCP ceph-admin:smc-https->ceph-admin:51474 (ESTABLISHED)
ceph-mds 29093 ceph    8u  IPv4  72642      0t0  TCP ceph-admin:51474->ceph-admin:smc-https (ESTABLISHED)

5)client端挂载ceph存储(采用fuse方式)

安装ceph-fuse(这里的客户机是centos6系统)
[root@centos6-02 ~]# rpm -Uvh https://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
[root@centos6-02 ~]# yum install -y ceph-fuse

创建挂载目录
[root@centos6-02 ~]# mkdir /cephfs

复制配置文件
将ceph配置文件ceph.conf从管理节点copy到client节点(192.168.10.220为管理节点)
[root@centos6-02 ~]# rsync -e "ssh -p22" -avpgolr root@192.168.10.220:/etc/ceph/ceph.conf /etc/ceph/
或者
[root@centos6-02 ~]# rsync -e "ssh -p22" -avpgolr root@192.168.10.220:/home/cephuser/cluster/ceph.conf /etc/ceph/    #两个路径下的文件内容一样

复制密钥
将ceph的ceph.client.admin.keyring从管理节点copy到client节点
[root@centos6-02 ~]# rsync -e "ssh -p22" -avpgolr root@192.168.10.220:/etc/ceph/ceph.client.admin.keyring /etc/ceph/
或者
[root@centos6-02 ~]# rsync -e "ssh -p22" -avpgolr root@192.168.10.220:/home/cephuser/cluster/ceph.client.admin.keyring /etc/ceph/

查看ceph授权
[root@centos6-02 ~]# ceph auth list
installed auth entries:

mds.ceph-admin
    key: AQAZZxdbH6uAOBAABttpSmPt6BXNtTJwZDpSJg==
    caps: [mds] allow
    caps: [mon] allow profile mds
    caps: [osd] allow rwx
osd.0
    key: AQCuWBdbV3TlBBAA4xsAE4QsFQ6vAp+7pIFEHA==
    caps: [mon] allow profile osd
    caps: [osd] allow *
osd.1
    key: AQC6WBdbakBaMxAAsUllVWdttlLzEI5VNd/41w==
    caps: [mon] allow profile osd
    caps: [osd] allow *
osd.2
    key: AQDJWBdbz6zNNhAATwzL2FqPKNY1IvQDmzyOSg==
    caps: [mon] allow profile osd
    caps: [osd] allow *
client.admin
    key: AQCNWBdbf1QxAhAAkryP+OFy6wGnKR8lfYDkUA==
    caps: [mds] allow *
    caps: [mon] allow *
    caps: [osd] allow *
client.bootstrap-mds
    key: AQCNWBdbnjLILhAAT1hKtLEzkCrhDuTLjdCJig==
    caps: [mon] allow profile bootstrap-mds
client.bootstrap-mgr
    key: AQCOWBdbmxEANBAAiTMJeyEuSverXAyOrwodMQ==
    caps: [mon] allow profile bootstrap-mgr
client.bootstrap-osd
    key: AQCNWBdbiO1bERAARLZaYdY58KLMi4oyKmug4Q==
    caps: [mon] allow profile bootstrap-osd
client.bootstrap-rgw
    key: AQCNWBdboBLXIBAAVTsD2TPJhVSRY2E9G7eLzQ==
    caps: [mon] allow profile bootstrap-rgw


将ceph集群存储挂载到客户机的/cephfs目录下
[root@centos6-02 ~]# ceph-fuse -m 192.168.10.220:6789 /cephfs
2018-06-06 14:28:54.149796 7f8d5c256760 -1 init, newargv = 0x4273580 newargc=11
ceph-fuse[16107]: starting ceph client
ceph-fuse[16107]: starting fuse

[root@centos6-02 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos602-lv_root
                       50G  3.5G   44G   8% /
tmpfs                 1.9G     0  1.9G   0% /dev/shm
/dev/vda1             477M   41M  412M   9% /boot
/dev/mapper/vg_centos602-lv_home
                       45G   52M   43G   1% /home
/dev/vdb1              20G  5.1G   15G  26% /data/osd1
ceph-fuse              45G  100M   45G   1% /cephfs

由上面可知,已经成功挂载了ceph存储,三个osd节点,每个节点有15G(在节点上通过"lsblk"命令可以查看ceph data分区大小),一共45G!

取消ceph存储的挂载
[root@centos6-02 ~]# umount /cephfs

温馨提示:
当有一半以上的OSD节点挂掉后,远程客户端挂载的Ceph存储就会使用异常了,即暂停使用。比如本案例中有3个OSD节点,当其中一个OSD节点挂掉后(比如宕机),
客户端挂载的Ceph存储使用正常;但当有2个OSD节点挂掉后,客户端挂载的Ceph存储就不能正常使用了(表现为Ceph存储目录下的数据读写操作一直卡着状态),
当OSD节点恢复后,Ceph存储也会恢复正常使用。OSD节点宕机重新启动后,osd程序会自动起来(通过监控节点自动起来)