2

Is possible to use Pacemaker failover without hardware?

  1. On quickstart http://clusterlabs.org/quickstart-redhat.html you can find the followowing commands: ccs -f /etc/cluster/cluster.conf --addfencedev pcmk agent=fence_pcmk

  2. Similar here: http://clusterlabs.org/quickstart-ubuntu.html <fencedevice name="pcmk" agent="fence_pcmk"/>

What is fence device? Is it hardware?

Added

According to the answer below, it is not possible to implement fencing without hardware. We want to use failover, but we do not want to use power card or something like this. Is it possible to implement failover without without fencing?

Alternatively, can we use as a fencing device the UDP / TCP connections?

Michael
  • 597
  • 3
  • 9
  • 23

1 Answers1

1

What you ask for is cluster fencing without hardware.

Fencing is a mechanism that avoids cluster inconsistency by killing (usually using power off) the member which we cannot tell about its state with certainty. This is usually done by using devices, like UPS or other power control devices that can forcibly terminate the dubious node.

I only know about hardware devices for this job however some people say that it can be done using libvirt in a virtualized cluster on KVM hypervisor, for example.

trikelef
  • 518
  • 1
  • 7
  • 26
  • Thanks for the answer (+1)! So, it is not possible to implement fencing without hardware. Is it possible to implement failover without without fencing? – Michael Jun 06 '13 at 09:59
  • I'd say it is possible to implement fencing without hardware using the utilites of a hypervisor platform like the libvirt as said above. About failover without fencing, I would say it is not so dangerous to not having fencing, except for the case where the resource you failover manages data and definitelly should ensure data integrity, eg when you use DBRD in your cluster. Eg if nodes use DRDB to write data on a filesystem, then you should kill/power off immediatelly a node when it goes in an uncertain state, before another node (failover) starts servicing the requests. – trikelef Jun 06 '13 at 14:06
  • 1
    Thanks for the comment, but hypervisor is not good for us. We just want to install 2 Centos computers and to configure HA using one virtual IP. Is it possible with Pacemaker? – Michael Jun 06 '13 at 14:54
  • Yes of course it is... – trikelef Jun 06 '13 at 15:02
  • Will happy if you will confirm me I should start with this configuration: http://clusterlabs.org/doc/en-US/Pacemaker/1.1-plugin/html-single/Clusters_from_Scratch/index.html#_perform_a_failover – Michael Jun 07 '13 at 05:13