OpenSearch and Prometheus storage sizing


Calculations in this document are based on numbers from a real-scale test cluster with 34 nodes. The exact space required for metrics and logs must be calculated depending on the ongoing cluster operations. Some operations force the generation of additional metrics and logs. The values below are approximate. Use them only as recommendations.

During the deployment of a new cluster, you must specify the OpenSearch retention time and Persistent Volume Claim (PVC) size, Prometheus PVC, retention time, and retention size. When configuring an existing cluster, you can only set OpenSearch retention time, Prometheus retention time, and retention size.

The following table describes the recommendations for both OpenSearch and Prometheus retention size and PVC size for a cluster with 34 nodes. Retention time depends on the space allocated for the data. To calculate the required retention time, use the {retention time} = {retention size} / {amount of data per day} formula.


Required space per day



StackLight in non-HA mode:
  • 202 - 253 GB for the entire cluster

  • ~6 - 7.5 GB for a single node

StackLight in HA mode:
  • 404 - 506 GB for the entire cluster

  • ~12 - 15 GB for a single node

When setting Persistent Volume Claim Size for OpenSearch during the cluster creation, take into account that it defines the PVC size for a single instance of the OpenSearch cluster. StackLight in HA mode has 3 OpenSearch instances. Therefore, for a total OpenSearch capacity, multiply the PVC size by 3.


  • 11 GB for the entire cluster

  • ~400 MB for a single node

Every Prometheus instance stores the entire database. Multiple replicas store multiple copies of the same data. Therefore, treat the Prometheus PVC size as the capacity of Prometheus in the cluster. Do not sum them up.

Prometheus has built-in retention mechanisms based on the database size and time series duration stored in the database. Therefore, if you miscalculate the PVC size, retention size set to ~1 GB less than the PVC size will prevent disk overfilling.