Recovery settings deprecated in 1.x have been removed:
* `index.shard.recovery.translog_size` is superseded by `indices.recovery.translog_size`
* `index.shard.recovery.translog_ops` is superseded by `indices.recovery.translog_ops`
* `index.shard.recovery.file_chunk_size` is superseded by `indices.recovery.file_chunk_size`
* `index.shard.recovery.concurrent_streams` is superseded by `indices.recovery.concurrent_streams`
* `index.shard.recovery.concurrent_small_file_streams` is superseded by `indices.recovery.concurrent_small_file_streams`
* `indices.recovery.max_size_per_sec` is superseded by `indices.recovery.max_bytes_per_sec`
If you are using any of these settings please take the time to review their
purpose. All of the settings above are considered _expert settings_ and should
only be used if absolutely necessary. If you have set any of the above setting
as persistent cluster settings please use the settings update API and set
their superseded keys accordingly.
The following settings have been removed without replacement
* `indices.recovery.concurrent_small_file_streams` - recoveries are now single threaded. The number of concurrent outgoing recoveries are throttled via allocation deciders
* `indices.recovery.concurrent_file_streams` - recoveries are now single threaded. The number of concurrent outgoing recoveries are throttled via allocation deciders
==== Translog settings
The `index.translog.flush_threshold_ops` setting is not supported anymore. In
order to control flushes based on the transaction log growth use
`index.translog.flush_threshold_size` instead.
Changing the translog type with `index.translog.fs.type` is not supported
anymore, the `buffered` implementation is now the only available option and
uses a fixed `8kb` buffer.
The translog by default is fsynced after every `index`, `create`, `update`,
`delete`, or `bulk` request. The ability to fsync on every operation is not
necessary anymore. In fact, it can be a performance bottleneck and it's trappy
since it enabled by a special value set on `index.translog.sync_interval`.
Now, `index.translog.sync_interval` doesn't accept a value less than `100ms`
which prevents fsyncing too often if async durability is enabled. The special
value `0` is no longer supported.
==== Request Cache Settings
The deprecated settings `index.cache.query.enable` and
`indices.cache.query.size` have been removed and are replaced with
`index.requests.cache.enable` and `indices.requests.cache.size` respectively.
`indices.requests.cache.clean_interval has been replaced with
`indices.cache.clean_interval and is no longer supported.
==== Field Data Cache Settings
The `indices.fielddata.cache.clean_interval` setting has been replaced with
`indices.cache.clean_interval`.
==== Allocation settings
The `cluster.routing.allocation.concurrent_recoveries` setting has been
replaced with `cluster.routing.allocation.node_concurrent_recoveries`.
==== Similarity settings
The 'default' similarity has been renamed to 'classic'.
==== Indexing settings
The `indices.memory.min_shard_index_buffer_size` and
`indices.memory.max_shard_index_buffer_size` have been removed as
Elasticsearch now allows any one shard to use amount of heap as long as the
total indexing buffer heap used across all shards is below the node's
`indices.memory.index_buffer_size` (defaults to 10% of the JVM heap).
==== Removed es.max-open-files
Setting the system property es.max-open-files to true to get
Elasticsearch to print the number of maximum open files for the
Elasticsearch process has been removed. This same information can be
obtained from the <<cluster-nodes-info>> API, and a warning is logged