# AOSPERF03-BP01 Establish storage utilization thresholds
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 Maintain efficient resource utilization by keeping domain storage usage under 75% to prevent potential performance issues or cluster write blocks. 

 **Level of risk exposed if this best practice is not established:** High 

 **Desired outcome**: Domain storage usage remains below 75%, which improves resource utilization and minimizes potential performance issues due to storage constraints. 

 **Benefits of establishing this best practice:** You can prevent write operations such as adding documents or creating indices to fail. 

## Implementation guidance
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 If one or more data nodes in your cluster have storage space less than the minimum value of either 20% of available storage space or 20 GB, basic write operations such as adding documents and creating indexes may fail. 
+  The Amazon CloudWatch `FreeStorageSpace` metric is used to monitor available storage in the data nodes. 
+  Adjusting your indexing rate or deleting unnecessary data can help keep your storage usage below the set threshold. 
+  If you are using UltraWarm nodes, consider migrating logs and time-series indices from the hot storage to the UltraWarm nodes. 

### Implementation steps
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+  Log in to the AWS Management Console. 
+  Navigate to the Amazon OpenSearch Service console. 
+  Select your OpenSearch Service domain name. 
+  Choose the **Cluster health** tab. 
+  Navigate to the Data nodes box. 
+  Choose the `FreeStorageSpace` graph. 
+  Adjust time range to `2w` and Statistic to `Maximum`. 
+  Remove unnecessary or redundant data from your domain. Use the `GET _cat/indices` API to list and investigate your indices and the `DELETE /<index_name>` API to remove unnecessary or redundant data. 
+  Consider adding more storage to your domain by increasing EBS storage size or add more data nodes to your domain. Keep this step consistent with shard-to-CPU ratio, shard-to-java-heap ratio, and shards distribution across your domain. For more information, see [AOSPERF01-BP01](aosperf01-bp01.md), [AOSPERF01-BP02](aosperf01-bp02.md), and [AOSPERF03-BP02](aosperf03-bp02.md). 
+  For more detail, see [Lack of available storage space](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/handling-errors.html#troubleshooting-cluster-block). 

## Resources
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+  [Monitoring OpenSearch cluster metrics with Amazon CloudWatch](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/managedomains-cloudwatchmetrics.html#managedomains-cloudwatchmetrics-box-charts) 
+  [Choosing the number of shards](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/bp-sharding.html) 
+  [Sizing OpenSearch Service domains](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/sizing-domains.html) 
+  [Lack of available storage](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/handling-errors.html#troubleshooting-cluster-block)