Why is the SysMemoryUtilization so high on my Amazon OpenSearch Service cluster?

Last updated: 2021-07-23

I noticed that the SysMemoryUtilization on my Amazon OpenSearch Service (successor to Amazon Elasticsearch Service) cluster is above 90%. Why is my system memory utilization usage so high?


System memory utilization that is above 90% doesn't indicate any heap usage issues or an overloaded OpenSearch Service cluster. A system memory utilization above 90% is considered normal, especially for nodes running OpenSearch Service. Therefore, you don't need to scale up the size of your cluster.

Most of the memory used by OpenSearch Service is for in-memory data structures. OpenSearch Service uses off-heap buffers for efficient and fast access to files. The Java virtual machine (JVM) also requires some memory.

To determine whether your cluster needs to be scaled up, use an Amazon CloudWatch alarm on these metrics:

  • JVM memory pressure
  • CPU utilization
  • Free storage space

For more information about setting CloudWatch alarms, see Recommended CloudWatch alarms.

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