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What does it mean?
To backup Elasticsearch indices you need to use the Elasticsearch snapshot mechanism. It is not sufficient to have backups of the individual data directories of the data nodes, because if you were to restore these directories there is no guarantee that the data recovered would form a consistent copy of the cluster. At best, data could be lost, and at worst it could be impossible to restore the cluster entirely.
How to resolve
Specific Installation Instructions will depend on the plugin / storage system used. The basic steps required are:
- Create a storage container with your chosen provider (like fs, cloud storage, etc)
- Create access credentials to access the storage container using your provider
- Install the required plugin on each Elasticsearch node
- Add the access credentials to each Elasticsearch node
- Create the repository in the cluster using the required Elasticsearch command.
Upon creation, the repository is verified automatically on all nodes. If this verification fails, then the repository creation command will raise an error.
If you want to manually verify a repository you can also run:
Detailed instructions for creating a repository on a shared mounted file system can be found here: https://www.elastic.co/guide/en/elasticsearch/reference/current/snapshots-register-repository.html
You can also find information about using plugins for alternative storage methods here: https://www.elastic.co/guide/en/elasticsearch/plugins/master/index.htm