Why is the default value of the shared_buffers DB parameter for Aurora PostgreSQL higher than the default value for Amazon RDS PostgreSQL?
I want to understand the differences between default values of DB parameter groups for Amazon Aurora PostgreSQL and Amazon Relational Database Service (Amazon RDS) PostgreSQL?
"I want to understand the differences between default values of DB parameter groups for Amazon Aurora PostgreSQL and Amazon Relational Database Service (Amazon RDS) PostgreSQL?ResolutionPostgreSQL recommends using a reasonable starting value for shared_buffers of 25% of the memory in your system. However, you can change this value depending on your workload requirements. To find an appropriate value for shared_buffers for your workload, see the PostgreSQL documentation for Resource Consumption.PostgreSQL relies heavily on the operating system for its caching (double buffering). As a result, allocating more than 40% of RAM to shared_buffers is unlikely to perform better than a smaller value.For RDS DB instances, the default value of the DB parameter group is set to 25% of total memory. For Aurora DB instances, the default value of the DB parameter group is set between 50% and 75%, depending on the instance class. Default values for Aurora DB instances are higher because Aurora PostgreSQL eliminates double buffering and doesn't utilize file system cache. As a result, Aurora PostgreSQL can increase shared_buffers to improve performance. It's a best practice to use the default value of 75% for the shared_buffers DB parameter when using Aurora PostgreSQL. A smaller value can degrade performance by reducing the available memory to the data pages while also increasing I/O on the Aurora storage subsystem. For more information, see Amazon Aurora PostgreSQL reference.Note: You might need to reduce the value of the shared_buffers parameter for some workloads. For example, you might need to reduce the value if your workload accepts a large number of connections that is higher than the default value, or if you frequently use larger work_mem, maintenance_work_mem, and so on. However, a smaller value for shared_buffers means that the cache hit ratio is also lower. As a result, you might see an increase in access latency for database pages because of frequent storage access.Related informationWorking with parameter groupsFollow"