How To Solve Issues Related to Log – Low disk watermark exceeded on ; replicas will not be assigned to this node

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Troubleshooting Background – start here to get the full picture       
Related Issues – selected resources on related issues  
Log Context – usefull for experts
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Troubleshooting background

To troubleshoot Elasticsearch log “Low disk watermark exceeded on ; replicas will not be assigned to this node” it’s important to know common problems related to Elasticsearch concepts: allocation, cluster, monitor, node, routing, threshold. See below-detailed explanations complete with common problems, examples and useful tips.

Cluster in Elasticsearch

What is it

In Elasticsearch a cluster is a collection of one or more nodes (servers / VMs). A cluster can consist of an unlimited number of nodes. The cluster provides interface for indexing and storing data and search capability across all of the data which is stored in the data nodes

Each cluster has a single master node that is elected by the master eligible nodes. In cases where the master is not available the other connected master eligible nodes elect a new master. Clusters are identified by a unique name, which defaults to “Elasticsearch”.


To help troubleshoot related issues we have gathered selected Q&A from the community and issues from Github , please review the following for further information :

low disk watermark [??%] exceeded on
stackoverflow.com/questions/33369955/low-disk-watermark-exceeded-on

Number of Views : 54.99 K  Score on Stackoverflow : 55

High disk watermark exceeded even when there is not much data in my index
stackoverflow.com/questions/30289024/high-disk-watermark-exceeded-even-when-there-is-not-much-data-in-my-index

Number of Views : 35.92 K  Score on Stackoverflow : 35


Log Context

Log ”Low disk watermark exceeded on ; replicas will not be assigned to this node” classname is DiskThresholdMonitor.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

<pre class="wp-block-syntaxhighlighter-code">                 diskThresholdSettings.getFreeBytesThresholdFloodStage(); usage);
        } else if (usage.getFreeBytes() < diskThresholdSettings.getFreeBytesThresholdHigh().getBytes()) {
            logger.warn("high disk watermark [{}] exceeded on {}; shards will be relocated away from this node";
                diskThresholdSettings.getFreeBytesThresholdHigh(); usage);
        } else if (usage.getFreeBytes() < diskThresholdSettings.getFreeBytesThresholdLow().getBytes()) {
            logger.info("low disk watermark [{}] exceeded on {}; replicas will not be assigned to this node";
                diskThresholdSettings.getFreeBytesThresholdLow(); usage);
        }

        // Check percentage disk values
        if (usage.getFreeDiskAsPercentage() < diskThresholdSettings.getFreeDiskThresholdFloodStage()) {




</pre>

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