Why is AWS Aurora Write IOS high at all times?-CodePudding

In AWS RDS Aurora - Monitoring section we notice that, even though most time there is no database activity (according to Monitoring and Performance Insights),

We still notice that for the past weeks,

Aurora Write IOPS was high at all times
Aurora Write Latency was high at all times (multiple 100s of ms to seconds)

Why could this be? What could caue the Write IOPS saturation? There is no Database activity that we can see.

CodePudding user response：

Open a connection to the Aurora instance and search for long running queries:

SELECT
  pid,
  now() - pg_stat_activity.query_start AS duration,
  query,
  state
FROM pg_stat_activity
WHERE (now() - pg_stat_activity.query_start) > interval '5 minutes';

This will show you any queries that you can then kill.

If it doesn't reveal any queries then something seems wrong with the instance. I would stop and start the instance to see if the behavior changes.

CodePudding user response：

In case of AWS Aurora, the writes are done only in memory and to the storage cluster. Inspecting the write latency on the storage cluster, using SSD, is 1ms per write. It is still concerning that the EBS (in our case) write latency on the DB instance is high but the database storage (logs, pages) is not on instances disk or volume or EBS, but only in discs on the storage cluster. So it is a bit less concerning and less impacting on the INSERT or COMMIT latency.