Fix: AWS RDS Storage Full — Database Unresponsive

!Symptoms

• Database queries timing out or failing
• RDS console showing storage at 100%
• Error: 'could not extend file' or 'No space left on device'
• Application errors related to database writes failing

?Root Causes

• Storage auto-scaling not enabled or max limit reached
• Large transaction logs (WAL/binlog) not being purged
• Bloated tables from missing VACUUM (PostgreSQL) or OPTIMIZE (MySQL)
• Large temporary tables from inefficient queries
• Excessive snapshots or point-in-time recovery logs

#Diagnosis Steps

1. 1Check storage: AWS Console → RDS → Instance → Storage section
2. 2Check CloudWatch: `FreeStorageSpace` metric approaching zero
3. 3For PostgreSQL: `SELECT pg_database_size(current_database());` and `SELECT pg_size_pretty(pg_total_relation_size(relid)) FROM pg_catalog.pg_statio_user_tables ORDER BY pg_total_relation_size(relid) DESC LIMIT 10;`
4. 4Check WAL size: `SELECT pg_size_pretty(pg_wal_lsn_diff(pg_current_wal_lsn(), '0/0'));`
5. 5For MySQL: `SHOW TABLE STATUS;` and check Data_length + Index_length

>Fix

1. 1Enable storage auto-scaling: `aws rds modify-db-instance --db-instance-identifier <id> --max-allocated-storage 500`
2. 2Manually increase storage: `aws rds modify-db-instance --allocated-storage <new-size>` (one-way, cannot decrease)
3. 3Run VACUUM FULL on bloated PostgreSQL tables
4. 4Delete old snapshots if not needed for compliance
5. 5Kill long-running queries generating temp tables: `SELECT pg_terminate_backend(pid)`

*Prevention

• Always enable storage auto-scaling with a sensible max limit
• Set CloudWatch alarms for FreeStorageSpace below 20%
• Schedule regular VACUUM/ANALYZE for PostgreSQL via pg_cron
• Monitor table bloat and set up automated cleanup
• Use RDS Performance Insights to catch queries generating excessive temp data

Related Error Messages