Credit system on RDS Postgresql gp3 volumes

0

Hi,

Recently we switched from a gp2 volume to a gp3 in our PostgreSQL RDS databases, which is almost 4tb so over the 400gb for the 12000 IOPS minimum baseline.

Still we are seeing the credit metrics on the cloudwatch monitoring tab, and apparently it seems the old 3k to 4k limit to use credits are still being applied when IOPS loads are over the old limits.

According to the documentation, no credit system is applied to gp3 PostgreSQL RDS volumes and only the baseline limit (12k IOPS) is applied: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Storage.html

Why is the credits metrics still showing and RDS is still using the old limits?

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Réponse acceptée

Hi,

I've seen cases for the same, because this volume was GP2 earlier, the BurstBalance metric is still reported to CloudWatch. BurstBalance is only valid for gp2,st1 and sc1 volume types and also depends upon the volume specifications, like size.

Ideally the metric shouldn't affect the performance even if the balance drops, you can ignore the metric.

However, If you are experiencing performance degradation + able to see the credits drop in cloudwatch + in gp3, you can open up a case with support to verify the GP3 state of the volumes internally.

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  • This is interesting! We have the exact same case. A volume that was gp2 earler and got converted to gp3. Our EBSByteBalance% is still visible and dropping despite the sum of read and write throughput only reaching around 5 to 7 MiB/s so well within the specified baseline of the gp3 volume. The problem is that or DB restarts once the credits reach zero. This has happened several times over the last few days and while it's only a testing DB it's still annoying as we are currently filling up the DB with data and need to restart those jobs after every DB reboot... So in this case I will open a support ticket as all my efforts are doomed to fail if it is indeed a bug...

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