elasticsearch/docs/reference/modules/indices/recovery.asciidoc

[[recovery]]
=== Indices Recovery

<<cat-recovery,Peer recovery>> is the process used to build a new copy of a
shard on a node by copying data from the primary. {es} uses this peer recovery
process to rebuild shard copies that were lost if a node has failed, and uses
the same process when migrating a shard copy between nodes to rebalance the
cluster or to honor any changes to the <<modules-cluster,shard allocation
settings>>.

The following _expert_ setting can be set to manage the resources consumed by
peer recoveries:

`indices.recovery.max_bytes_per_sec`::
    Limits the total inbound and outbound peer recovery traffic on each node.
    Since this limit applies on each node, but there may be many nodes
    performing peer recoveries concurrently, the total amount of peer recovery
    traffic within a cluster may be much higher than this limit. If you set
    this limit too high then there is a risk that ongoing peer recoveries will
    consume an excess of bandwidth (or other resources) which could destabilize
    the cluster. Defaults to `40mb`.

`indices.recovery.max_concurrent_file_chunks`::
    Controls the number of file chunk requests that can be sent in parallel per recovery.
    As multiple recoveries are already running in parallel (controlled by
    cluster.routing.allocation.node_concurrent_recoveries), increasing this expert-level
    setting might only help in situations where peer recovery of a single shard is not
    reaching the total inbound and outbound peer recovery traffic as configured by
    indices.recovery.max_bytes_per_sec, but is CPU-bound instead, typically when using
    transport-level security or compression. Defaults to `2`.

This setting can be dynamically updated on a live cluster with the
<<cluster-update-settings,cluster-update-settings>> API.