[CentOS] KVM HA
lists at alteeve.ca
Wed Jun 22 17:47:45 UTC 2016
On 22/06/16 01:38 PM, John R Pierce wrote:
> On 6/21/2016 10:01 PM, Tom Robinson wrote:
>> Currently when I migrate a guest, I can all too easily start it up on
>> both hosts! There must be some
>> way to fence these off but I'm just not sure how to do this.
> in addition to power fencing as described by others, you can also fence
> at the ethernet switch layer, where you disable the switch port(s) that
> the dead host is on. this of course requires managed switches that your
> cluster management software can talk to. if you're using dedicated
> networking for ISCSI (often done for high performance), you can just
> disable that port.
This is called "fabric fencing" and was originally the only supported
option in the very early days of HA. It has fallen out of favour for
several reasons, but it does still work fine. The main issues is that it
leaves the node in an unclean state. If an admin (out of ignorance or
panic) reconnects the node, all hell can break lose. So generally power
cycling is much safer.
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