Doublewrite Buffer Write Amplification

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Resource ContentionUpdated Jun 8, 2023

InnoDB's doublewrite buffer causes additional write operations that can saturate provisioned IOPS and increase latency. Each 16KB page write to data files requires a prior write to the doublewrite buffer, creating overhead that scales with write-heavy workloads.

Sources

Monitoring RDS MySQL performance metrics | Datadogwww.datadoghq.com

Improve application performance on Amazon RDS for MySQL and MariaDB instances and MySQL Multi-AZ DB clusters with Optimized Writes | Amazon Web Services Database Blogwww.amazonaws.cn

Technologies:

MariaDBThe root cause of this issue originates in MariaDB

How to detect:

Monitor the ratio of innodb_dblwr_writes to innodb_data_writes. High write IOPS consumption with elevated innodb_dblwr_writes and WriteLatency indicates doublewrite buffer overhead. If WriteLatency rises while approaching IOPS limits, and innodb_dblwr_writes is significant, the doublewrite buffer may be the bottleneck.

Recommended action:

If running on RDS for MySQL 8.0.30+ or MariaDB 10.6.10+ on supported Nitro instance classes, enable RDS Optimized Writes by setting rds.optimized_writes=AUTO. This disables the doublewrite buffer by providing torn-write protection at the hardware layer. For older versions or unsupported instances, increase provisioned IOPS, optimize queries to reduce write volume, or upgrade to a supported configuration.