Does the Read IOPS metric on RDS count OS cache hits?



  • I'm doing some tuning on a read-only replica, and I want to make sure I understand the "Read IOPS" metric. Certainly, any pages that are found in the postgres shared_buffers cache don't contribute to it. And certainly, any reads that have to go to the actual SSD do contribute. But what about reads that are handled by the operating system's disk cache? I assume they do not contribute to that metric, but I can't find any documentation on the AWS site that verifies it. Does anyone know for certain?



  • I also contacted AWS support and they confirmed that reads from the disk cache don't contribute to the Read IOPs metric.




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