25.05.2018 14:44, Klaus Wenninger пишет: > On 05/25/2018 12:44 PM, Andrei Borzenkov wrote: >> On Fri, May 25, 2018 at 10:08 AM, Klaus Wenninger <kwenn...@redhat.com> >> wrote: >>> On 05/25/2018 07:31 AM, 井上 和徳 wrote: >>>> Hi, >>>> >>>> I am checking the watchdog function of SBD (without shared block-device). >>>> In a two-node cluster, if one cluster is stopped, watchdog is triggered on >>>> the remaining node. >>>> Is this the designed behavior? >>> SBD without a shared block-device doesn't really make sense on >>> a two-node cluster. >>> The basic idea is - e.g. in a case of a networking problem - >>> that a cluster splits up in a quorate and a non-quorate partition. >>> The quorate partition stays over while SBD guarantees a >>> reliable watchdog-based self-fencing of the non-quorate partition >>> within a defined timeout. >> Does it require no-quorum-policy=suicide or it decides completely >> independently? I.e. would it fire also with no-quorum-policy=ignore? > > Finally it will in any case. But no-quorum-policy decides how > long this will take. In case of suicide the inquisitor will immediately > stop tickling the watchdog. In all other cases the pacemaker-servant > will stop pinging the inquisitor which will makes the servant > timeout after a default of 4 seconds and then the inquisitor will > stop tickling the watchdog. > But that is just relevant if Corosync doesn't have 2-node enabled. > See the comment below for that case. > >> >>> This idea of course doesn't work with just 2 nodes. >>> Taking quorum info from the 2-node feature of corosync (automatically >>> switching on wait-for-all) doesn't help in this case but instead >>> would lead to split-brain. >> So what you are saying is that SBD ignores quorum information from >> corosync and takes its own decisions based on pure count of nodes. Do >> I understand it correctly? > > Yes, but that is just true for this case where Corosync has 2-node > enabled. > > In all other cases (might it be clusters with more than 2 nodes > or clusters with just 2 nodes but without 2-node enabled in > Corosync) pacemaker-servant takes quorum-info from > pacemaker, which will probably come directly from Corosync > nowadays. > But as said if 2-node is configured with Corosync everything > is different: The node-counting is then actually done > by the cluster-servant and this one will stop pinging the > inquisitor (instead of the pacemaker-servant) if it doesn't > count more than 1 node. >
Is it conditional on having no shared device or it just checks two_node value? If it always behaves this way, even with real shared device present, it means sbd is fundamentally incompatible with two_node and it better be mentioned in documentation. > That all said I've just realized that setting 2-node in Corosync > shouldn't really be dangerous anymore although it doesn't make > the cluster especially useful either in case of SBD without disk(s). > > Regards, > Klaus _______________________________________________ Users mailing list: Users@clusterlabs.org https://lists.clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
