8RedHat6 集群Fence

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RedHat6 集群Fence

实验目的:

掌握集群Fence理论和配置

 

Fence概念:

在HA集群坏境中,备份服务器B通过心跳线来发送数据包来看服务器A是否还活着,主服务器A接收了大量的客户端访问请求,服务器A的CPU负载达到100%响应不过来了,资源已经耗尽,没有办法回复服务器B数据包(回复数据包会延迟),这时服务器B认为服务器A已经挂了,于是备份服务器B把资源夺过来,自己做主服务器,过了一段时间服务器A响应过来了,服务器A觉得自己是老大,服务器B觉得自己也是老大,他们两个就挣着抢夺资源,集群资源被多个节点占有,两个服务器同时向资源写数据,破坏了资源的安全性和一致性,这种情况的发生叫做“脑裂”。服务器A负载过重,响应不过来了,有了Fence机制,Fence会自动的把服务器A给Fence掉,阻止了“脑裂"的发生

 

Fence分类:

硬件Fence:电源Fence,通过关掉电源来踢掉坏的服务器

软件Fence:Fence卡(智能卡),通过线缆、软件来踢掉坏的服务器

 

实际坏境中,Fence卡连接的都是专线,使用专用的Fence网卡,不会占用数据传输线路,这样,更能保证稳定及可靠性。

Fence卡的IP网络和集群网络是相互依存的

 

实验步骤:

由于实际情况的限制,没有真实的Fence卡,所用我们用fence服务来虚拟出Fence卡

在iscsi服务器上安装fence服务,把iscsi服务器当成fence卡

 

安装fence卡,你只需要安装fence-virtd-libvirt.x86_64和fence-virtd-multicast.x86_64这两个软件就可以了

[root@node1 ~]# yum list  |  grep fence

Repository ResilientStorage is listed morethan once in the configuration

Repository ScalableFileSystem is listedmore than once in the configuration

fence-agents.x86_64                        3.1.5-10.el6                @Cluster

fence-virt.x86_64                          0.2.3-5.el6                 @Cluster

fence-virtd.x86_64                         0.2.3-5.el6                 base    

fence-virtd-checkpoint.x86_64              0.2.3-5.el6                 Cluster 

fence-virtd-libvirt.x86_64                 0.2.3-5.el6                 base    

fence-virtd-libvirt-qpid.x86_64            0.2.3-5.el6                 optional

fence-virtd-multicast.x86_64               0.2.3-5.el6                 base    

fence-virtd-serial.x86_64                  0.2.3-5.el6                 base  

[root@node1 ~]# yum  -y  install fence-virtd-libvirt.x86_64 fence-virtd-multicast.x86_64

[root@desktop24 ~]# mkdir /etc/cluster

[root@desktop24 ~]# cd /etc/cluster

[root@desktop24 cluster]# dd   if=/dev/random   of=/etc/cluster/fence_xvm.key  bs=4k  count=1   创建fence卡的key文件,让节点服务器和Fence卡相互认识

0+1 records in

0+1 records out

73 bytes (73 B) copied, 0.000315063 s, 232kB/s

 

random:为随机数字生成器,生成的东西是唯一的

fence_xvm.key:Fence卡的key文件,名字别改,fence_xvm是fence卡的一种类型

 

把fence的key文件分发给各个节点服务器

[root@desktop24cluster]#scp/etc/cluster/fence_xvm.key  172.17.0.1:/etc/cluster/fence_xvm.key

root@172.17.0.1's password:

fence_xvm.key                                                             100%   73     0.1KB/s  00:00   

[root@desktop24 cluster]# scp  /etc/cluster/fence_xvm.key   172.17.0.2:/etc/cluster/fence_xvm.key

root@172.17.0.2's password:

fence_xvm.key                                                             100%   73     0.1KB/s  00:00

 

 

 

对fence服务的配置文件/etc/fence_virt.conf做配置策略:

[root@desktop24 cluster]# fence_virtd   -c

Module search path[/usr/lib64/fence-virt]:

//模块搜索路径,回车使用默认的

Available backends:

   libvirt 0.1

Available listeners:

   multicast 1.1

 

Listener modules are responsible foraccepting requests

from fencing clients.

 

Listener module [multicast]:

//监听组播模块,回车选择默认

The multicast listener module is designedfor use environments

where the guests and hosts may communicateover a network using

multicast.

 

The multicast address is the address that aclient will use to

send fencing requests to fence_virtd.

 

Multicast IP Address[225.0.0.12]:

组播IP地址选择,回车选择默认的225.0.0.12

Using ipv4 as family.

 

Multicast IP Port [1229]:

//组播IP端口选择,回车选择默认的1229

Setting a preferred interface causes fence_virtdto listen only

on that interface.  Normally, it listens on all interfaces.

In environments where the virtual machinesare using the host

machine as a gateway, this *must* be set(typically to virbr0).

Set to 'none' for no interface.

 

Interface [none]: private

//Fence卡使用那个接口来和集群网络来通讯(fence卡的专用接口和集群网络在同一网段)

The key file is the shared key informationwhich is used to

authenticate fencing requests.  The contents of this file must

be distributed to each physical host andvirtual machine within

a cluster.

 

Key File[/etc/cluster/fence_xvm.key]:

//是否是对/etc/cluster/fence_xvm.key这个文件做策略,回车选择默认的

Backend modules are responsible for routingrequests to

the appropriate hypervisor or managementlayer.

 

Backend module [checkpoint]:libvirt

//模块基于那个协议,填写libvirt

The libvirt backend module is designed forsingle desktops or

servers. Do not use in environments where virtual machines

may be migrated between hosts.

 

Libvirt URI [qemu:///system]:

 

Configuration complete.

 

=== Begin Configuration ===

backends {

         libvirt{

                   uri= "qemu:///system";

         }

 

}

 

listeners {

         multicast{

                   interface= "eth0";

                   port= "1229";

                   family= "ipv4";

                   address= "225.0.0.12";

                   key_file= "/etc/cluster/fence_xvm.key";

         }

 

}

 

fence_virtd {

         module_path= "/usr/lib64/fence-virt";

         backend= "libvirt";

         listener= "multicast";

}

 

=== End Configuration ===

Replace /etc/fence_virt.confwith the above [y/N]? y

//输入y保存配置

 

启动fence服务:

[root@desktop24 cluster]# /etc/init.d/fence_virtd  restart

Stopping fence_virtd:                                      [FAILED]

Starting fence_virtd:                                      [  OK  ]

[root@desktop24 cluster]# chkconfig  fence_virtd on

 

 

 

fence卡加入到集群:

Fence Dervices中点击add来添加fence卡(虚拟的)

 

 

 

 

 

打开【Select  a  fence device】选择【Fence virt(Multicast  Mode)】,名字写这个Fence卡名字


虚拟的Fence设备添加完成后,界面如下:

 

Fence卡添加到各个节点中去

添加fence卡到Node1中:

 

选择【Node】,然后点击Node1节点的界面,找到下图位置添加Fence

 

取名根据自己需要,只要能识别即可

然后点击【Add Fence Instance】,添加Fence实咧

 

选择Fence1这个Fence卡,这里的domain指的的是node1.private.cluster0.example.com中的node1

 

 

添加Fence卡到Node2中:

把界面换到节点2中

 

找到下图位置,点击【Add  Fence  Method】

给Fence  Method起名字

点击【Add Fence Instance】

 

 

 

 

选择Fence1这个Fence卡,这里的domain指的的是node2.private.cluster0.example.com中的node2

 

 


 

 

 

手动fence剔除:

[root@node2 ~]# fence_node  node1

fence node1   success

实验效果:node1会重启两次

 

 

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