postgresql random_page_cost

[Paul Lamb]

Didn't find anyone asking about this already here or on stack overflow. I'm assuming that the default value of 4 is being used for random_page_cost (I created a new pg instance today with 2 cpu/13gb memory, 100gb of ssd). This might have just been overlooked but that's an awfully high number. Most of the time for more modern san's a number in the 1.5-2.0 is considered conservative. Also, how are are shared_buffers getting set? For this instance I created today it's set to have 128mb for shared buffers.

[Ankush Agarwal]

Paul,

Thank you for your feedback and for bringing up the random_page_cost parameter. We have filed a bug internally to investigate the performance impact of random_page_cost.

Regarding shared_buffers, we currently have a default of 128MB for instances having < 60G RAM and 1/3*ram_size for instances with > 60G RAM. We have also started investigating setting an optimal shared_buffers for instances with < 60G RAM. Please let us know if you have any other questions or concerns.

[Paul Lamb]

Please consider work_mem too, 4mb is awfully low too. I may be too used to custom tuning instances for my work load. I'd generally set work_mem closer to 30-35mb for a 12-16gb instance with 100 connections.

[Ankush Agarwal]

Thanks Paul, we'll look into work_mem as well

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Ankush Agarwal

Software Engineer, Cloud SQL

 

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