MySQL Replication: Seconds Behind Master keep growing We have set up a new slave server for our production database. Since than the Seconds_Behind_Master keep growing slowly.

This is the slave output:


           Slave_IO_State: Waiting for master to send event
              Master_Host: notimportant
              Master_User: repl
              Master_Port: 3306
            Connect_Retry: 60
          Master_Log_File: mysql-bin.003790
      Read_Master_Log_Pos: 42585179
           Relay_Log_File: mysqld-relay-bin.002798
            Relay_Log_Pos: 32374374
    Relay_Master_Log_File: mysql-bin.003492
         Slave_IO_Running: Yes
        Slave_SQL_Running: Yes
          Replicate_Do_DB: 
      Replicate_Ignore_DB: 
       Replicate_Do_Table: 
   Replicate_Ignore_Table: 
  Replicate_Wild_Do_Table:  
               Last_Errno: 0
               Last_Error: 
             Skip_Counter: 0
      Exec_Master_Log_Pos: 32374215
          Relay_Log_Space: 31350956440
          Until_Condition: None
           Until_Log_File: 
            Until_Log_Pos: 0
       Master_SSL_Allowed: No
       Master_SSL_CA_File: 
       Master_SSL_CA_Path: 
          Master_SSL_Cert: 
        Master_SSL_Cipher: 
           Master_SSL_Key: 
    Seconds_Behind_Master: 1448477
            Last_IO_Errno: 0
            Last_IO_Error: 
           Last_SQL_Errno: 0
         Master_Server_Id: 6524
              Master_UUID: 
         Master_Info_File: /var/lib/mysql/master.info
                SQL_Delay: 0
      SQL_Remaining_Delay: NULL
  Slave_SQL_Running_State: Reading event from the relay log
       Master_Retry_Count: 86400
              Master_Bind: 
  Last_IO_Error_Timestamp: 
 Last_SQL_Error_Timestamp: 
           Master_SSL_Crl: 
       Master_SSL_Crlpath: 
       Retrieved_Gtid_Set: 
        Executed_Gtid_Set: 
            Auto_Position: 0



Show processlist on SLAVE:

|    1 | system user |           | NULL | Connect | 2143813 | Waiting for master to send event | NULL             |
|    2 | system user |           | NULL | Connect | 1448477 | Reading event from the relay log | NULL             |
| 1628 | root        | localhost | NULL | Query   |       0 | init                             | SHOW PROCESSLIST |


On MASTER side:

|  7947837 | repl       | host-vm:59420     | NULL          | Binlog Dump | 2143817 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL             |


On MASTER the show slave hosts:

+-----------+------+------+-----------+
| Server_id | Host | Port | Master_id |
+-----------+------+------+-----------+
|      3410 |      | 3410 |      6524 |
| 347643210 |      | 3306 |      6524 |
+-----------+------+------+-----------+


Does anyone has an idea what's going on and how can I fix it?
The solution was to add the following to my.cnf:

innodb_flush_log_at_trx_commit = 2


Our server was slow in I/O and the row above reduced the disk usage.

It is not recommended for bank databases, but recommended to all others.

Phrased differently:  =1 flushes at then end of each transaction, thereby making it ACID-compliant.  =2 flushes to disk every second, thereby being much less I/O-intensive.