Manually Scale up/down single cluster - without OMC

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
Currently using Opensearch and opensearch-dashboard at 2.11.1 and operator version 2.3.0

Describe the issue:
According to documentation of OMC, it says that it is smooth to manage multiple clusters. In my scenario, we are having a single cluster with 3 master nodes with role of data & cluster_manager assigned to them.

I tried to integrate the OMC but the image being used in the helm repo of OMC: has lot of critical vulnerability issues reported using trivy scan so we cannot use this image in our env as it is private repository where we need to replicate the publicly available image.

So, as an alternative, I need to know how to manually scale up the cluster without using the fancy OMC as it is for single cluster?
how to calculate the resource requirement based on the data load size?


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