Support for multiple data paths removed in Elasticsearch v8

Elastic are removing the ability to provide multiple data paths (MDP) in Elasticsearch 8. This is a potentially major breaking change for some customers and I would strongly suggest working on mitigation plans ahead of the release.

Elasticsearch currently has the ability to provide multiple data paths in the elasticsearch.yml configuration file. This allows Elasticsearch to spread the node’s data over multiple paths - even disks if configured accordingly - and I’ve spoken to users who have applied this configuration to help with disk IO.

The configuration below, for example, would spread the node’s data over three paths:

node.name: ${HOSTNAME}
path.data:
  - /mnt/elasticsearch_1
  - /mnt/elasticsearch_2
  - /mnt/elasticsearch_3

This configuration will throw an error when Elasticsearch 8 starts.

I can see this change causing a lot of pain for customers who use MDP. Elastic’s argument for removing support is that MDP isn’t well understood by the community, isn’t widely used, and causes a lot of headaches with development and testing. The discussion on the GitHub issue got a fairly negative response. I don’t expect the change to have the gravity that the removal of document types did, but it’s still not going down well.

The pull request merging the change is here.