elasticsearch/docs/reference/path-settings-overview.asciidoc

[[path-settings-overview]]
=== Path settings

include::{es-ref-dir}/setup/important-settings/path-settings.asciidoc[]

[[multiple-data-paths]]
==== Multiple data paths
deprecated::[7.13.0]

If needed, you can specify multiple paths in `path.data`. {es} stores the node's
data across all provided paths but keeps each shard's data on the same path.

{es} does not balance shards across a node's data paths. High disk
usage in a single path can trigger a <<disk-based-shard-allocation,high disk
usage watermark>> for the entire node. If triggered, {es} will not add shards to
the node, even if the node’s other paths have available disk space. If you need
additional disk space, we recommend you add a new node rather than additional
data paths.

include::{es-ref-dir}/tab-widgets/multi-data-path-widget.asciidoc[]

[[mdp-migrate]]
===== Migrate from multiple data paths

Support for multiple data paths was deprecated in 7.13 and will be removed
in a future release.

As an alternative to multiple data paths, you can create a filesystem which
spans multiple disks with a hardware virtualisation layer such as RAID, or a
software virtualisation layer such as Logical Volume Manager (LVM) on Linux or
Storage Spaces on Windows. If you wish to use multiple data paths on a single
machine then you must run one node for each data path.

If you currently use multiple data paths in a
{ref}/high-availability-cluster-design.html[highly available cluster] then you
can migrate to a setup that uses a single path for each node without downtime
using a process similar to a
{ref}/restart-cluster.html#restart-cluster-rolling[rolling restart]: shut each
node down in turn and replace it with one or more nodes each configured to use
a single data path. In more detail, for each node that currently has multiple
data paths you should follow the following process. In principle you can
perform this migration during a rolling upgrade to 8.0, but we recommend
migrating to a single-data-path setup before starting to upgrade.

1. Take a snapshot to protect your data in case of disaster.

2. Optionally, migrate the data away from the target node by using an
{ref}/modules-cluster.html#cluster-shard-allocation-filtering[allocation filter]:
+
[source,console]
--------------------------------------------------
PUT _cluster/settings
{
  "persistent": {
    "cluster.routing.allocation.exclude._name": "target-node-name"
  }
}
--------------------------------------------------
+
You can use the {ref}/cat-allocation.html[cat allocation API] to track progress
of this data migration. If some shards do not migrate then the
{ref}/cluster-allocation-explain.html[cluster allocation explain API] will help
you to determine why.

3. Follow the steps in the
{ref}/restart-cluster.html#restart-cluster-rolling[rolling restart process]
up to and including shutting the target node down.

4. Ensure your cluster health is `yellow` or `green`, so that there is a copy
of every shard assigned to at least one of the other nodes in your cluster.

5. If applicable, remove the allocation filter applied in the earlier step.
+
[source,console]
--------------------------------------------------
PUT _cluster/settings
{
  "persistent": {
    "cluster.routing.allocation.exclude._name": null
  }
}
--------------------------------------------------

6. Discard the data held by the stopped node by deleting the contents of its
data paths.

7. Reconfigure your storage. For instance, combine your disks into a single
filesystem using LVM or Storage Spaces. Ensure that your reconfigured storage
has sufficient space for the data that it will hold.

8. Reconfigure your node by adjusting the `path.data` setting in its
`elasticsearch.yml` file. If needed, install more nodes each with their own
`path.data` setting pointing at a separate data path.

9. Start the new nodes and follow the rest of the
{ref}/restart-cluster.html#restart-cluster-rolling[rolling restart process] for
them.

10. Ensure your cluster health is `green`, so that every shard has been
assigned.

You can alternatively add some number of single-data-path nodes to your
cluster, migrate all your data over to these new nodes using
{ref}/modules-cluster.html#cluster-shard-allocation-filtering[allocation filters],
and then remove the old nodes from the cluster. This approach will temporarily
double the size of your cluster so it will only work if you have the capacity to
expand your cluster like this.

If you currently use multiple data paths but your cluster is not highly
available then you can migrate to a non-deprecated configuration by taking
a snapshot, creating a new cluster with the desired configuration and restoring
the snapshot into it.