AWS RDS Memory - Why RAM mentioned in Cloudwatch metrics is less the the RAM for instance db.r4.8xlarge

Question

Hi,
We are using db.r4.8xlarge instance to host our MySQL cluster. Whenever we reboot the instance and check the Cloudwatch metrics for freeable memory , its shows max memory around 52 GB. But as per the instance type, the total RAM provided in 244 GB.
Can someone please explain how this works and is something wrong with our configuration.

Thanks

Answer

Hi,

Thank you for your question.

Aurora MySQL `innodb_buffer_pool_size` parameter is set by default to 75 percent of physical memory. So, db.r4.8xlarge instance initially available nearly 61GB memory.  You can also change the memory settings, but please do a performance test before/after modify this parameter.

This [document](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/CHAP_Troubleshooting.html#Troubleshooting.FreeableMemory) explain how to identify Freeable memory issues in Amazon Aurora.

I hope this might help.

AWS RDS Memory - Why RAM mentioned in Cloudwatch metrics is less the the RAM for instance db.r4.8xlarge

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