On 09/07/15 03:27, renayama19661014@xxxxxxxxx wrote:
> Hi All,
>
> We compose a cluster of the following setting in corosync and Pacemaekr.
>
> quorum {
> provider: corosync_votequorum
> expected_votes: 2
> }
>
> expected_votes increases by the increase of the node.
> Is this setting that does not increase possible?
> * It looks like specifications to increase as far as it sees a manual.
>
> When a cluster does not control QUORUM, is it necessary to set expected_votes to the number of the nodes?
> * It seems to be necessary to set the number of all nodes by all means in expected_votes when I read the next description.
>
> ---man/votequorum.5.html---
> (snip)
> votequorum reads its configuration from corosync.conf. Some values can be changed at runtime, others are only read at corosync startup. It is very important that those values are consistent across all the nodes participating in the cluster or votequorum behavior will be unpredictable.
>
> votequorum requires an expected_votes value to function, this can be provided in two ways. The number of expected votes will be automatically calculated when the nodelist { } section is present in corosync.conf or expected_votes can be specified in the quorum { } section. Lack of both will disable votequorum. If both are present at the same time, the quorum.expected_votes value will override the one calculated from the nodelist.
> Example (no nodelist) of an 8 node cluster (each node has 1 vote):
>
> quorum {
> provider: corosync_votequorum
> expected_votes: 8
> }
> (snip)
>
> However, I think that it is not necessary to set it because expected_votes increases automatically.
> In other words, does expected_votes not necessarily have to set it with the number of all nodes if control of QUORUM is invalid without using nodelist?
>
expected_votes is needed for the quorum calculation. If the list of all
cluster nodes is present in corosync.conf then that is used to calculate
the expected votes so that the cluster will know when less than half of
the nodes are available.
If there is no nodes list then then (without expected_votes) any node
does not know whether it is part of quorate partition or not (eg it
could start isolated or in a cluster of 2, not knowing there are 5 other
nodes it cannot see).
So it is extremely important to set expected_votes when not using the
nodelist.
You are correct that expected_votes will increase (internally, it's not
automatically stored in corosync.conf - that's why it should be
distributed) as nodes are added, this is to guard against future
potential cluster splits.
Chrissie
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