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From: Eden Aharoni <[email protected]>
To: [email protected] <[email protected]>
Subject: RDS IO Read time
Date: Mon, 31 Mar 2025 13:54:20 +0000
Message-ID: <DBBPR03MB102227BDDC40A11527BF6C0C0BBAD2@DBBPR03MB10222.eurprd03.prod.outlook.com> (raw)

Hi all,
Hopefully, someone here could help us understand whats going on with our deployment..
We are running Postgres 17.4 on AWS RDS on an ec2 instance that has:

  *   32vCPU
  *   128GB RAM
  *   gp3 with 25K IOPS and 4000MiB/s throughput
  *   the instance supports up to 3125GB/s of throughput.
Whenever a query fetches data from the disk (index scan, bitmap scans, etc.) we’re reaching 23 – 30MB/s of IO Read time.
We changed our autovacuum settings to be more aggressive (0 scale factor and 10K threshold) so our index only scans will (hopefully) read data from the disk rarely. However, we can’t optimize all the queries to use index-only-scan since our users can dynamically select which columns to see and filtering.
Is this expected IO read rate? I can’t help but feel we’re missing something here..

Thanks a lot! 😊

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