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In an Elasticsearch cluster, must all nodes be identical i.e. having the same:

  • Operating System
  • Amount of RAM
  • CPU speed and number of cores
  • etc.

or is it allowed for the nodes to be different? (Apart from the obvious fact that an homogeneous cluster would be much easier to configure, manage, and monitor than an heterogeneous one.)

3 Answers 3

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It depends. They don't need to be identical in hardware resources. But they should be identical in OS (at least linux distribution or windows version) and must be identical in ES version.

ES doesn't support running multiple versions of ES in one cluster for long time because indices created or migrated on higher version cannot be migrated back to older version (due internal data mechanics and so on), so you will be in trouble when node with newer version will fail.

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In an Elasticsearch cluster, must all nodes be identical i.e. having the same: or is it allowed for the nodes to be different?

No, they do not need to be identical. Depending on use case of the cluster, and the roles assigned to each node, hardware differences are to be expected.

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  • Could you please elaborate a bit your answer? Drawbacks, etc.?
    – dr_
    Mar 23, 2016 at 16:33
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    Would you like me to write a book? :) Honestly, your question is far too broad to get into details.
    – EEAA
    Mar 23, 2016 at 16:34
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The ElasticSearch nodes do not need to be the same, aside from running a compatible ES version. Since queries often span multiple ES nodes then you'll be beholden to the slowest node, and the differences will make it hard to tune.

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    you'll be beholden to the slowest node actually, if you set it up right, this is very false. It's not uncommon to have older, slower hardware backing seldom used indices. It's possible to use routing to make sure the hottest indices are one the best hardware, just as it's possible to setup the opposite.
    – GregL
    Mar 23, 2016 at 20:18
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    I agree, if one goes to the effort to map indices to node performance. I was thinking of the default behavior where such mapping wasn't done. Mar 23, 2016 at 20:46

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