Upgrading 1.x to 7.5

I've inherited a product that still uses Elasticsearch 1.x (don't ask!) and would like to upgrade to 7.5. From reading the documentation it seems that:

  • upgrading from one major version to another is possible without a reindex
  • but to upgrade further would require a reindex

So the sequence of upgrades I'd have to perform would be:

  1. 1.x => 2.x in place, no reindex
  2. 2.x => 5.x requires a reindex
  3. 5.x => 6..x in place, no reindex
  4. 6.x => 7.5 reindex

can someone confirm?



Elasticsearch and Lucene only support indices one major version down, so you are missing some reindexing steps and there are 2 options to upgrade:

  • The most simple way is to install a new cluster in 7.5 and remote reindex from the version 1 cluster.
  • If you want to upgrade version after version (the only reason to do that would be lack of resources to install a second cluster, it is going to take more time/effort), you will want : upgrade to 2.4.latest, reindex, upgrade to 5.6.latest, reindex, upgrade to 6.8.latest, reindex, upgrade to 7.5.latest and reindex (last reindex optional till you upgrade to version 8.x). Also in 5.6 and above you can use the migration assistant in kibana to help you with the other steps (enabling deprecation logs, migrating system indices and checking there is no old indices to reindex)


Great, thanks Julien - we can afford to spin up a new cluster, so remote reindex seems like the easiest approach.

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