77 lines
3.2 KiB
Plaintext
77 lines
3.2 KiB
Plaintext
[[disk-allocator]]
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=== Disk-based Shard Allocation
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Elasticsearch factors in the available disk space on a node before deciding
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whether to allocate new shards to that node or to actively relocate shards
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away from that node.
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Below are the settings that can be configured in the `elasticsearch.yml` config
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file or updated dynamically on a live cluster with the
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<<cluster-update-settings,cluster-update-settings>> API:
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`cluster.routing.allocation.disk.threshold_enabled`::
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Defaults to `true`. Set to `false` to disable the disk allocation decider.
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`cluster.routing.allocation.disk.watermark.low`::
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Controls the low watermark for disk usage. It defaults to 85%, meaning ES will
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not allocate new shards to nodes once they have more than 85% disk used. It
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can also be set to an absolute byte value (like 500mb) to prevent ES from
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allocating shards if less than the configured amount of space is available.
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`cluster.routing.allocation.disk.watermark.high`::
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Controls the high watermark. It defaults to 90%, meaning ES will attempt to
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relocate shards to another node if the node disk usage rises above 90%. It can
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also be set to an absolute byte value (similar to the low watermark) to
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relocate shards once less than the configured amount of space is available on
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the node.
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NOTE: Percentage values refer to used disk space, while byte values refer to
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free disk space. This can be confusing, since it flips the meaning of high and
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low. For example, it makes sense to set the low watermark to 10gb and the high
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watermark to 5gb, but not the other way around.
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`cluster.info.update.interval`::
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How often Elasticsearch should check on disk usage for each node in the
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cluster. Defaults to `30s`.
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`cluster.routing.allocation.disk.include_relocations`::
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Defaults to +true+, which means that Elasticsearch will take into account
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shards that are currently being relocated to the target node when computing a
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node's disk usage. Taking relocating shards' sizes into account may, however,
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mean that the disk usage for a node is incorrectly estimated on the high side,
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since the relocation could be 90% complete and a recently retrieved disk usage
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would include the total size of the relocating shard as well as the space
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already used by the running relocation.
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An example of updating the low watermark to no more than 80% of the disk size, a
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high watermark of at least 50 gigabytes free, and updating the information about
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the cluster every minute:
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[source,js]
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--------------------------------------------------
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PUT /_cluster/settings
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{
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"transient": {
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"cluster.routing.allocation.disk.watermark.low": "80%",
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"cluster.routing.allocation.disk.watermark.high": "50gb",
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"cluster.info.update.interval": "1m"
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}
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}
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--------------------------------------------------
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// AUTOSENSE
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NOTE: Prior to 2.0.0, when using multiple data paths, the disk threshold
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decider only factored in the usage across all data paths (if you had two
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data paths, one with 50b out of 100b free (50% used) and another with
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40b out of 50b free (80% used) it would see the node's disk usage as 90b
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out of 150b). In 2.0.0, the minimum and maximum disk usages are tracked
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separately.
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