Binlog (binary log) files are used to replicate data from the Master database to the replica database. All statements that modify data, like
delete statements, cause a line to be added to the MySQL binlogs. Queries that only read from the database, without changing the contents, do not add a line to the binlogs. In addition, staging environments which don't have redundant databases still use binlogs, which helps keep feature and performance parity between non-production and production environments.
If binlog files are created too rapidly it can cause the disk to become full. This can happen due to:
- A large database import
- An influx of
CACHEstatements, as they contain serialized data, which can be addressed by using memcached
- Web crawlers requesting uncached pages
INSERTs due to the Dblog module, which should be disabled in favor of the Syslog module
If MySQL can no longer write to the binlog files, it cannot process
writes and MySQL will lock up. In some cases,
reads may still work.
Acquia monitors disk utilization and notifies customers when binlog files are filling disk volumes too quickly.