# When server A is turned off, then servers B and C are not available. This is normal? **URL:** \ **Category:** Elasticsearch\ **Created:** [May 14, 2018, 9:57am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709 "2018-05-14T09:57:14Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![clgs](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/clgs/32/48363_2.png) [@clgs](https://discuss.elastic.co/u/clgs)\ **Post date:** [May 14, 2018, 9:57am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/1 "2018-05-14T09:57:14Z")
Hi. We have three servers (A, B and C). Server A must be made a master. Servers B and C with slaves. Server A: node.master: true node.data: true node.ingest: false discovery.zen.ping.unicast.hosts: ["A", "B", "C"] Server B node.master: false node.data: true node.ingest: false discovery.zen.ping.unicast.hosts: ["B", "C", "A"] Server C node.master: false node.data: true node.ingest: false discovery.zen.ping.unicast.hosts: ["C", "A", "B"] When server A is turned off, then servers B and C are not available. This is normal? ---
**Author:** ![A\_B](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/a_b/32/17104_2.png) [@A\_B](https://discuss.elastic.co/u/A_B)\ **Post date:** [May 14, 2018, 10:08am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/2 "2018-05-14T10:08:00Z")
If you only have one `master` I think that is what happens. Why can't B and C be masters? ---
**Author:** ![rcowart](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/rcowart/32/88091_2.png) [@rcowart](https://discuss.elastic.co/u/rcowart)\ **Post date:** [May 14, 2018, 10:14am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/3 "2018-05-14T10:14:08Z")
`node.master: true` means that the node is "master eligible", not that it will be THE master. For a three node cluster you need... ```auto Server A: node.master: true node.data: true node.ingest: false discovery.zen.ping.unicast.hosts: ["B", "C"] discovery.zen.minimum_master_nodes: 2 Server B node.master: true node.data: true node.ingest: false discovery.zen.ping.unicast.hosts: ["C", "A"] discovery.zen.minimum_master_nodes: 2 Server C node.master: true node.data: true node.ingest: false discovery.zen.ping.unicast.hosts: ["A", "B"] discovery.zen.minimum_master_nodes: 2 ``` ---
**Author:** ![clgs](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/clgs/32/48363_2.png) [@clgs](https://discuss.elastic.co/u/clgs)\ **Post date:** [May 14, 2018, 10:15am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/4 "2018-05-14T10:15:09Z")
Do the wizards B and C, and write data only on A? It is assumed that A is RW, B and C are only R. ---
**Author:** ![A\_B](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/a_b/32/17104_2.png) [@A\_B](https://discuss.elastic.co/u/A_B)\ **Post date:** [May 14, 2018, 10:16am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/5 "2018-05-14T10:16:31Z")
That is not what `node.master` means... The master role has to do with managing the cluster nodes. All nodes will be RW. And `node.data` is what sets if documents are stored on the node or not. ---
**Author:** ![clgs](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/clgs/32/48363_2.png) [@clgs](https://discuss.elastic.co/u/clgs)\ **Post date:** [May 14, 2018, 10:16am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/6 "2018-05-14T10:16:32Z")
Or to make all servers node.master: true? ---
**Author:** ![A\_B](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/a_b/32/17104_2.png) [@A\_B](https://discuss.elastic.co/u/A_B)\ **Post date:** [May 14, 2018, 10:19am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/7 "2018-05-14T10:19:06Z")
> [@clgs](#): > > Or to make all servers node.master: true? yes 😃 ---
**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\ **Post date:** [May 14, 2018, 10:19am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/8 "2018-05-14T10:19:40Z")
Even easier start your nodes with the only following configuration: ```auto discovery.zen.ping.unicast.hosts: ["A", "B", "C"] discovery.zen.minimum_master_nodes: 2 ``` ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [May 14, 2018, 10:23am UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/9 "2018-05-14T10:23:29Z")
Elasticsearch nodes form a cluster, it is not a master-slave architecture. ---
**Author:** ![A\_B](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/a_b/32/17104_2.png) [@A\_B](https://discuss.elastic.co/u/A_B)\ **Post date:** [May 14, 2018, 3:40pm UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/10 "2018-05-14T15:40:00Z")
> [@rcowart](#): > > Server A: > node.master: true > node.data: true > node.ingest: false > discovery.zen.ping.unicast.hosts: ["B", "C"] > discovery.zen.minimum\_master\_nodes: 2 > > Server B > node.master: true > node.data: true > node.ingest: false > discovery.zen.ping.unicast.hosts: ["C", "A"] > discovery.zen.minimum\_master\_nodes: 2 > > Server C > node.master: true > node.data: true > node.ingest: false > discovery.zen.ping.unicast.hosts: ["A", "B"] > discovery.zen.minimum\_master\_nodes: 2 Is this config not a little bit dangerous? Not listing the "local" node in `discovery.zen.ping.unicast.hosts` that is. When ever any node goes down `discovery.zen.minimum_master_nodes: 2` is not true anymore... Say, node **A** goes down for any reason. - **A** can not be master (it is stopped) - **B** can not be elected master as it will need an answer from both **C** and **A** for who should be elected master - **C** can not be elected master as it will need an answer from both **A** and **B** for who should be elected master I'm just curious... Maybe I don't know something about master election. ---
**Author:** ![clgs](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/clgs/32/48363_2.png) [@clgs](https://discuss.elastic.co/u/clgs)\ **Post date:** [May 14, 2018, 3:55pm UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/11 "2018-05-14T15:55:34Z")
**dadoonet** write: ``` discovery.zen.ping.unicast.hosts: ["A", "B", "C"] discovery.zen.minimum_master_nodes: 2 ``` ---
**Author:** ![rcowart](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/rcowart/32/88091_2.png) [@rcowart](https://discuss.elastic.co/u/rcowart)\ **Post date:** [May 14, 2018, 4:37pm UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/12 "2018-05-14T16:37:45Z")
No it doesn't need an answer from both of those. B already knows about his own configuration, he just needs to find another master eligible node and he is good to go. So as long as A or C are reachable (in you example C would be), there is a 2 node quorum and all is well. B doesn't have to send a unicast message to himself. @dadoonet was just arguing in favor of consistency on all three nodes. Either way works. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [June 11, 2018, 4:37pm UTC](https://discuss.elastic.co/t/when-server-a-is-turned-off-then-servers-b-and-c-are-not-available-this-is-normal/131709/13 "2018-06-11T16:37:51Z")
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