Confusing info on RDS gp3 pricing

When moving from gp2 to gp3 for your PostgreSQL RDS instance, there are a few key pricing aspects to understand.

For gp3 volumes, you get a baseline performance of 3,000 IOPS and 125 MB/s throughput included in the base storage price. This baseline is free - you only pay extra if you provision additional performance beyond this baseline.

However, there's an important limitation for RDS PostgreSQL specifically: gp3 volumes must be at least 400 GB to allow customizing IOPS and throughput. At that size, you can provision IOPS in the range of 12,000-64,000 and throughput from 500-4,000 MiB/s, but you will pay for the additional performance above the baseline.

So in your case, moving to a 400 GB gp3 volume:

1. You'll pay for the base 400 GB storage at the gp3 rate (which is about 20% less expensive per GB than gp2)
2. You'll get 3,000 IOPS and 125 MB/s included for free
3. If you provision additional IOPS (above 3,000), you'll pay $0.005 per provisioned IOPS-month
4. If you provision additional throughput (above 125 MB/s), you'll pay $0.04 per provisioned MB/s-month

The 12,000 IOPS and 500 MB/s you mentioned are the minimum configurable values for a 400 GB PostgreSQL RDS instance using gp3, not what's included for free. You would need to pay for 9,000 additional IOPS (12,000 - 3,000) and 375 MB/s additional throughput (500 - 125).

This explains why the AWS calculator shows a substantial price increase - you're paying for those additional performance capabilities beyond the free baseline.
Sources
High-Performance Block Storage– Amazon EBS Pricing – Amazon Web Services
Optimize Amazon RDS costs for predictable workloads with automated IOPS and throughput scaling | AWS Database Blog
Migrate Amazon EBS volumes from gp2 to gp3 - AWS Prescriptive Guidance

Hi,

Please refer to the below Amazon RDS DB instance storage documentation which provides detailed information regarding baseline IOPS performance for different RDS DB engines including RDS PostgreSQL, especially the table with Storage size and Baseline storage performance.

When the RDS PostgreSQL allocated storage is between 400–65,536 GiB, the baseline IOPS is 12,000 IOPS/500 MiB/s due to volume striping into 4 volumes instead of 1 which gives 3000 IOPS * 4 = 12,000 IOPS baseline performance. Again, you pay for only the additional provisioned storage performance and not for baseline performance.

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Storage.html#Concepts.Storage.GeneralSSD

While GP2 also has storage striping for volumes 400GB and above, but the baseline is 1,200-4,005 IOPS with burst up to 12,000 IOPS which is also referenced in the same document.

Hello,

Thanks for your prompt reply!

I hope you are right. The cost calculator (https://calculator.aws/#/createCalculator/EBS) seems to 'think' differently though.

Peter

Hello

I don't have access to this price calculator it seems

And the messaging is still confusing to me:

With gp3 volumes, you can configure storage, IOPS and throughput independently and will be charged for the resources you consume **above the baseline**. **gp3 volumes have a baseline performance of 3,000 IOPS and 125 MB/s throughput**.

Again thank you for your time!

Peter

Ok...nm. I could type in the url from your screenshot and see what you are seeing :)

I will just trust this last calculator and jump

Tx!!