# Recommended number of master eligible nodes in a cluster
**URL:** https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627
**Category:** Elasticsearch
**Created:** [January 14, 2015, 8:38am UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627 "2015-01-14T08:38:01Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Darshat\_Shah](https://discuss.elastic.co/u/Darshat_Shah)
#### Post date: [January 14, 2015, 8:38am UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/1 "2015-01-14T08:38:01Z")
Hi,
What is the guideline on recommended number of master eligible nodes in a
cluster?
We have a big cluster with 90+ nodes, currently all are eligible to be
masters. However I do see master election take very long after a cluster
restart - most nodes are still trying to ping the old master and I think
there is no way to force a re-election.
Will re-election be faster if number of master eligible nodes be less? Is
there a rule of thumb, given N nodes how many should we configure to be
eligible to be masters?
Thanks
Darshat
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### Author:  [@drjz](https://discuss.elastic.co/u/drjz)
#### Post date: [January 14, 2015, 8:46am UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/2 "2015-01-14T08:46:27Z")
The formula is N/2+1, so in your case that would be 46 if there are 90
nodes.
/JZ
On Wednesday, January 14, 2015 at 9:38:01 AM UTC+1, Darshat Shah wrote:
> Hi,
> What is the guideline on recommended number of master eligible nodes in a
> cluster?
>
> We have a big cluster with 90+ nodes, currently all are eligible to be
> masters. However I do see master election take very long after a cluster
> restart - most nodes are still trying to ping the old master and I think
> there is no way to force a re-election.
>
> Will re-election be faster if number of master eligible nodes be less? Is
> there a rule of thumb, given N nodes how many should we configure to be
> eligible to be masters?
>
> Thanks
> Darshat
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### Author:  [@Darshat\_Shah](https://discuss.elastic.co/u/Darshat_Shah)
#### Post date: [January 14, 2015, 8:54am UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/3 "2015-01-14T08:54:28Z")
That's the minimum number. Is it recommended to have more, or will
elections take longer if we have more than this minimum?
On Wednesday, January 14, 2015 at 2:16:27 PM UTC+5:30, drjz wrote:
> The formula is N/2+1, so in your case that would be 46 if there are 90
> nodes.
>
> /JZ
>
> On Wednesday, January 14, 2015 at 9:38:01 AM UTC+1, Darshat Shah wrote:
>
> > Hi,
> > What is the guideline on recommended number of master eligible nodes in a
> > cluster?
> >
> > We have a big cluster with 90+ nodes, currently all are eligible to be
> > masters. However I do see master election take very long after a cluster
> > restart - most nodes are still trying to ping the old master and I think
> > there is no way to force a re-election.
> >
> > Will re-election be faster if number of master eligible nodes be less? Is
> > there a rule of thumb, given N nodes how many should we configure to be
> > eligible to be masters?
> >
> > Thanks
> > Darshat
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### Author:  [@Darshat\_Shah](https://discuss.elastic.co/u/Darshat_Shah)
#### Post date: [January 14, 2015, 9:39am UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/4 "2015-01-14T09:39:47Z")
To clarify, the guideline I'm looking for is how many nodes to set apart as
dedicated to be master eligible in a cluster of size N. That is not N/2+1.
On Wednesday, January 14, 2015 at 2:24:29 PM UTC+5:30, Darshat Shah wrote:
> That's the minimum number. Is it recommended to have more, or will
> elections take longer if we have more than this minimum?
>
> On Wednesday, January 14, 2015 at 2:16:27 PM UTC+5:30, drjz wrote:
>
> > The formula is N/2+1, so in your case that would be 46 if there are 90
> > nodes.
> >
> > /JZ
> >
> > On Wednesday, January 14, 2015 at 9:38:01 AM UTC+1, Darshat Shah wrote:
> >
> > > Hi,
> > > What is the guideline on recommended number of master eligible nodes in
> > > a cluster?
> > >
> > > We have a big cluster with 90+ nodes, currently all are eligible to be
> > > masters. However I do see master election take very long after a cluster
> > > restart - most nodes are still trying to ping the old master and I think
> > > there is no way to force a re-election.
> > >
> > > Will re-election be faster if number of master eligible nodes be less?
> > > Is there a rule of thumb, given N nodes how many should we configure to be
> > > eligible to be masters?
> > >
> > > Thanks
> > > Darshat
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### Author:  [@Mark\_Harwood\_2](https://discuss.elastic.co/u/Mark_Harwood_2)
#### Post date: [January 14, 2015, 12:17pm UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/5 "2015-01-14T12:17:33Z")
For installations like yours we would recommend 3 master eligible nodes.
This number doesn't need to scale with data volumes as your data nodes do.
A master eligible node should also be dedicated to that task alone - trying
to also fulfil search or indexing activities puts them at the risk of
becoming unresponsive.
We recommend 3 master-eligible nodes because that gives you both a
resiliency to failure and a necessary quorum required to avoid split-brain.
Fortunately master nodes can be lighter-weight machines than those
dedicated to search.
Anything less than 3 dedicated master-eligible nodes is essentially an
architectural compromise made for smaller-budget configurations.
On Wednesday, January 14, 2015 at 9:39:47 AM UTC, Darshat Shah wrote:
> To clarify, the guideline I'm looking for is how many nodes to set apart
> as dedicated to be master eligible in a cluster of size N. That is not
> N/2+1.
>
> On Wednesday, January 14, 2015 at 2:24:29 PM UTC+5:30, Darshat Shah wrote:
>
> > That's the minimum number. Is it recommended to have more, or will
> > elections take longer if we have more than this minimum?
> >
> > On Wednesday, January 14, 2015 at 2:16:27 PM UTC+5:30, drjz wrote:
> >
> > > The formula is N/2+1, so in your case that would be 46 if there are 90
> > > nodes.
> > >
> > > /JZ
> > >
> > > On Wednesday, January 14, 2015 at 9:38:01 AM UTC+1, Darshat Shah wrote:
> > >
> > > > Hi,
> > > > What is the guideline on recommended number of master eligible nodes in
> > > > a cluster?
> > > >
> > > > We have a big cluster with 90+ nodes, currently all are eligible to be
> > > > masters. However I do see master election take very long after a cluster
> > > > restart - most nodes are still trying to ping the old master and I think
> > > > there is no way to force a re-election.
> > > >
> > > > Will re-election be faster if number of master eligible nodes be less?
> > > > Is there a rule of thumb, given N nodes how many should we configure to be
> > > > eligible to be masters?
> > > >
> > > > Thanks
> > > > Darshat
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### Author:  [@Ed\_Kim](https://discuss.elastic.co/u/Ed_Kim)
#### Post date: [January 14, 2015, 7:22pm UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/6 "2015-01-14T19:22:58Z")
3 should be fine, and they don't even have to be beefy machines.
On Wednesday, January 14, 2015 at 1:39:47 AM UTC-8, Darshat Shah wrote:
> To clarify, the guideline I'm looking for is how many nodes to set apart
> as dedicated to be master eligible in a cluster of size N. That is not
> N/2+1.
>
> On Wednesday, January 14, 2015 at 2:24:29 PM UTC+5:30, Darshat Shah wrote:
>
> > That's the minimum number. Is it recommended to have more, or will
> > elections take longer if we have more than this minimum?
> >
> > On Wednesday, January 14, 2015 at 2:16:27 PM UTC+5:30, drjz wrote:
> >
> > > The formula is N/2+1, so in your case that would be 46 if there are 90
> > > nodes.
> > >
> > > /JZ
> > >
> > > On Wednesday, January 14, 2015 at 9:38:01 AM UTC+1, Darshat Shah wrote:
> > >
> > > > Hi,
> > > > What is the guideline on recommended number of master eligible nodes in
> > > > a cluster?
> > > >
> > > > We have a big cluster with 90+ nodes, currently all are eligible to be
> > > > masters. However I do see master election take very long after a cluster
> > > > restart - most nodes are still trying to ping the old master and I think
> > > > there is no way to force a re-election.
> > > >
> > > > Will re-election be faster if number of master eligible nodes be less?
> > > > Is there a rule of thumb, given N nodes how many should we configure to be
> > > > eligible to be masters?
> > > >
> > > > Thanks
> > > > Darshat
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### Author:  [@Matias\_Waisgold](https://discuss.elastic.co/u/Matias_Waisgold)
#### Post date: [January 14, 2015, 7:35pm UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/7 "2015-01-14T19:35:32Z")
I´ve created a 200 nodes cluster and successed with 3 master\_eligible
nodes. The important thing is that they have the data\_node setting in
false, and data\_nodes have it the other way around. This will improve a lot
your cluster resiliency.
On Wednesday, January 14, 2015 at 4:22:58 PM UTC-3, Ed Kim wrote:
> 3 should be fine, and they don't even have to be beefy machines.
>
> On Wednesday, January 14, 2015 at 1:39:47 AM UTC-8, Darshat Shah wrote:
>
> > To clarify, the guideline I'm looking for is how many nodes to set apart
> > as dedicated to be master eligible in a cluster of size N. That is not
> > N/2+1.
> >
> > On Wednesday, January 14, 2015 at 2:24:29 PM UTC+5:30, Darshat Shah wrote:
> >
> > > That's the minimum number. Is it recommended to have more, or will
> > > elections take longer if we have more than this minimum?
> > >
> > > On Wednesday, January 14, 2015 at 2:16:27 PM UTC+5:30, drjz wrote:
> > >
> > > > The formula is N/2+1, so in your case that would be 46 if there are 90
> > > > nodes.
> > > >
> > > > /JZ
> > > >
> > > > On Wednesday, January 14, 2015 at 9:38:01 AM UTC+1, Darshat Shah wrote:
> > > >
> > > > > Hi,
> > > > > What is the guideline on recommended number of master eligible nodes
> > > > > in a cluster?
> > > > >
> > > > > We have a big cluster with 90+ nodes, currently all are eligible to be
> > > > > masters. However I do see master election take very long after a cluster
> > > > > restart - most nodes are still trying to ping the old master and I think
> > > > > there is no way to force a re-election.
> > > > >
> > > > > Will re-election be faster if number of master eligible nodes be less?
> > > > > Is there a rule of thumb, given N nodes how many should we configure to be
> > > > > eligible to be masters?
> > > > >
> > > > > Thanks
> > > > > Darshat
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### Author:  [@xavierfacq](https://discuss.elastic.co/u/xavierfacq)
#### Post date: [October 11, 2016, 8:23pm UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/8 "2016-10-11T20:23:16Z")
Hi,
@Matias_Waisgold : With your cluster of 200 nodes with 3 master\_eligble, does all nodes vote for the master election or only masters ? If only masters vote, what is the configuration of above parameters ?
discovery.zen.minimum\_master\_nodes: 2 ==\> I think yes , doc says : (3 / 2 + 1)
discovery.zen.master\_election.filter\_data = true (only master vote )
Thank you !
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 5, 2017, 10:13pm UTC](https://discuss.elastic.co/t/recommended-number-of-master-eligible-nodes-in-a-cluster/21627/9 "2017-07-05T22:13:16Z")