On 06/11/13 20:44, Jason Harley wrote:
Hello —
I have a four node Corosync (2.3.0-1ubuntu4) cluster configured and happy.
However, I’d like to be able to allow the cluster to degrade to a single node
in an (extreme) failure state — but still require (at least) two nodes to
establish the cluster. Using qdisc is not an option in my environment, so I’m
curious if I can achieve this using new features in ‘Needle’ like
‘last_man_standing’ and ‘auto_tie_breaker’.
This is the ‘quorum’ block from my corosync.conf:
quorum {
provider: corosync_votequorum
expected_votes: 4
last_man_standing: 1
last_man_standing_window: 10000
auto_tie_breaker: 1
}
Is this as simple as telling votequorum that I have a two node cluster
(‘two_node: 1’) and enabling ‘allow_downscale’?
What you have should be fine with the addition of "wait_for_all: 1". You
probably don't auto_tie_breaker unless there is a likelihood of a 2+2
split on the network.
"two_node" means you have exactly 2 nodes in the cluster (not ever more)
so isn't relevant and allow_downscale is solving a different problem
than you have.
With last_man_standing the cluster will survive being degraded to 1 node
provided there is not a large outage and more than 2 nodes fail at a time.
the man page votequorum.5 has some good examples
Chrissie
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