Elasticsearch high disk watermark 90% exceeded on – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 1.7-1.7

Briefly, this error occurs when the disk usage on a node exceeds 90% of its total capacity. Elasticsearch uses watermarks to ensure that a node has enough disk space to operate normally. When the high disk watermark is exceeded, Elasticsearch will stop allocating new shards to that node. To resolve this issue, you can either increase the disk space, delete unnecessary indices or data, or adjust the disk watermark thresholds in the Elasticsearch settings. However, be cautious when adjusting the thresholds as it might lead to insufficient disk space for Elasticsearch operations.

Crossing high disk watermarks can be avoided if detected earlier. In addition we strongly recommend you run the Elasticsearch Error Check-Up. We found that 20% of people who ran the Check-Up failed this event. This free tool will detect issues in ES that cause many ES errors and specifically problems that causes disk space to run out quickly and prevent high disk watermark from exceeding.
The tool requires no installation and takes 2 minutes to complete. You can run the Check-Up here.

Log Context

Log “Elasticsearch high disk watermark [90%] exceeded on” classname is DiskThresholdDecider.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                                     entry; DiskThresholdDecider.this.rerouteInterval);
                if (reroute) {
                    logger.info("high disk watermark exceeded on one or more nodes; rerouting shards");
                    // Execute an empty reroute; but don't block on the response


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