“No space left on device” while AWS RDS Storage Auto Scaling Enabled

PostgreSQL RDS instance got “No space left on device” errors, even RDS storage auto scaling enabled. The storage can only be extended after at least 6 hours.

As for now,  although automatic scaling helps you to increase storage on your RDS instance dynamically, you should still configure the initial storage for your DB instance to an appropriate size for your typical workload.

Auto Scaling will kick in when these factors apply:

  • Free available space is less than 10 percent of the allocated storage.
  • The low-storage condition lasts at least five minutes.

We can also see, that the minimum the storage will increase is either 5GB or max 10% of your current allocated storage. That means that if you have an instance of 200Gb storage right now, your max ‘auto allocated’ storage space would be +20Gb of 200Gb which would be 220Gb. This will not be able to change for at least 6 hours.

Remember 6 hours policy when using “auto scaling”.