cloud database ai_generated true

RDS instance becomes read-only — storage full auto-scaling lag

ID: cloud/aws-rds-storage-full-readonly

Also available as: JSON · Markdown
85%Fix Rate
88%Confidence
4Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
any active — — —

Root Cause

RDS storage auto-scaling has a 6-hour cooldown. Instance goes read-only if storage fills between scaling events.

generic

Workarounds

  1. 90% success Set generous max storage threshold for auto-scaling with CloudWatch alarm at 80 percent 
    aws rds modify-db-instance --max-allocated-storage 500 --db-instance-identifier mydb

    Sources: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_PIOPS.StorageTypes.html

  2. 85% success Purge old data or archive to S3 to free space 
    DELETE FROM logs WHERE created_at < NOW() - INTERVAL 90 DAY;

    Sources: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_PIOPS.StorageTypes.html

Dead Ends

Common approaches that don't work:

  1. Manually increase storage during read-only state 60% fail

    Manual scaling is also subject to the 6-hour cooldown

  2. Restart the RDS instance to clear read-only 85% fail

    Restart does not free storage; instance goes read-only again immediately