[CentOS] Question about clustering

Wed Jun 18 18:14:20 UTC 2014
Digimer <lists at alteeve.ca>

On 18/06/14 12:32 PM, Alessandro Baggi wrote:
> Ok, fencing is a requirement for a cluster for hardware failure.
> I've  another question about this arg, but for software failure.
> Supposing to have a cluster of httpd installation on 6 virtualized
> hosts, each one on a different server. Suppose also that a guest (named
> host6) has a problem and can't start apache. With this scenario, the
> ipmi, ups are unnecessary. How to work fencing in this way? How to make
> fencing node?
> Thanks in advance.
> Alessandro.

I'm not sure I understand properly... You mean that you have 6 VMs which 
are nodes in a cluster, or 6 nodes, each hosting a VM you want to make HA?

If the VMs are themselves nodes, then you could use fence_virt as the 
primary fence method, which would power off/on the VM itself by talking 
to the hypervisor on the host. If that fails (say because the host 
itself fails), the use IPMI or PDU based fencing as a backup, in which 
case the host itself would be powered off/on (thus ensuring the VM on 
the host is down as well).

If the hardware servers themselves are the nodes, then the VMs are not a 
factor in the equation. Services, including VMs, will recover on another 
host after the fence has succeeded.

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