Binary Log Group Commit¶

In cases when strict durability and recoverability is required and the storage that provides fast syncs is unavailable, setting up the variables innodb_flush_log_at_trx_commit =1 and sync_binlog =1 can result in big performance drop.

Performance drop happening when these variables are enabled is caused by additional fsync() system calls on both binary and XtraDB REDO log when committing a transaction, that are needed to store the additional information on the disk. Binary Log Group Commit feature can use a single fsync() call to force data to the storage for multiple concurrently committing transactions, which provides throughput improvements in a write-concurrent workload.

Because there are no negative effects of this feature, it has been enabled by default and can’t be disabled. Effects of this feature can be measured by the binlog_commits and binlog_group_commits status variables. The bigger the difference between these two variables the bigger is the performance gained with this feature.