Fencing is a device. It will allow the cluster software to power on, power off, or restart the node remotely.
Why Fencing –maintain Data Integrity.
Without Fencing – Data Duplication (or) Data Corruption may occur.
HOW Fencing -- When any one of the node is not responding (or) time exceed to cman fencing will happened. Fencing is the process of isolating a node of a computer cluster or disconnects the node from the cluster Shared Storage.
it is like hardware come under /dev/ devices from the base machine.
Like /dev/kvm ,Console Devices /dev/ipmi0, or HP ILO
Referece Link: https://access.redhat.com/site/articles/28603
KVM Fencing
fence_virt > Fencing Agent for Virtual machine using VM Channel
fence_xvm > Fencing Agent for Virtual machine using Multicast
Method To Add Fence Device
1)Fence Device > Add > Fence Virt (Multicast Mode) > Give Name : KVM Fencing
2)choose node > Add Fence Method > Give Name: Method > Add Fence Instance > KVM_Fencing(xvm Virtual Machine Fencing)
For Cluster.conf file it will reflect in
Refer Link : http://www.studentcpu.com/2014/06/redhat-suite-high-availability-overview.html
<fence>
<method name="Method">
<device domain="node10" name="KVM_Fencing"/>
</method>
</fence>
<fencedevices>
<fencedevice agent="fence_xvm" name="KVM_Fencing"/>
</fencedevices>
3)Configure fence Daemon From Bash Machine.
bash-machine#fence_virt -c
https://alteeve.ca/w/Fencing_KVM_Virtual_Servers
#fence_xvm -H node10 (Command will trigger node10 to reboot)
# ccs_tool lsfence
Name Agent
KVM_Fencing fence_xvm
#ccs_tool lsnode
Cluster name: MY_CLUSTER2, config_version: 22
Nodename Votes Nodeid Fencetype
node10 1 1 KVM_Fencing
node11 1 2 KVM_Fencing
Fencing Method Vs Fencing Agent : https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/3/html/GFS_6.0_Administration_Guide/s1-fence-methods.html
Fencing Reference : http://clusterlabs.org/wiki/Guest_Fencing
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