do a show full processlist on the 4th slave and see what process is
running. This will the sql's running which will be the cause of the
slowness.

 

>> This does not help because there is not a specific query, which is
running slow. Other 3 slaves are running same query and I"ve compared
the explain on all slaves for most of the updates and they looks same.
All H/W and S/W config are same including the cnf file settings.

 

Also u need to check on the INTERNET bandwidth from the current data
center to the other data center.



>> This is also not an issue because IO thread is way ahead then SQL
thread. It's a  SQL thread, which is not able to keep up.  


 

On 6/18/08, Sagar, Sanjeev <[EMAIL PROTECTED]> wrote: 

Hello All,



I've 4 slaves of a master. Out of 4, 3 are in same data center and have
no issues. The fourth one is in another data center and some time that
slave sql_thread lag behind more then 5000 sec. It's only sql_thread,
which slow down. All H/W, S/W and my.cnf files are same for all slaves.



I ran the mysqladmin extended-status in iterative mode and following
kind of results are there in my log file



| Variable_name              | Value     |

+----------------------------+-----------+

| Bytes_received             | 2117975   |

| Com_insert                 | 39        |

| Com_show_slave_status      | 4         |

| Com_show_status            | 1         |

| Com_update                 | 49        |

| Connections                | 1         |

| Handler_read_key           | 49        |

| Handler_read_next          | 2         |

| Handler_update             | 3629      |

| Key_blocks_not_flushed     | 1         |

| Key_blocks_unused          | -21       |

| Key_blocks_used            | 21        |

| Key_reads                  | 21        |

| Key_write_requests         | 94        |

| Key_writes                 | 75        |

| Max_used_connections       | 1         |

| Questions                  | 93        |

| Table_locks_immediate      | 88        |

| Threads_connected          | 1         |

| Threads_created            | 1         |

+----------------------------+-----------+



+----------------------------+-----------+

| Variable_name              | Value     |

+----------------------------+-----------+

| Bytes_received             | 1469626   |

| Bytes_sent                 | 3837      |

| Com_delete                 | 2         |

| Com_insert                 | 143       |

| Com_show_status            | 1         |

| Com_update                 | 1247      |

| Handler_delete             | 5         |

| Handler_read_key           | 1249      |

| Handler_read_next          | 73        |

| Handler_read_rnd           | 8379      |

| Handler_update             | 9625      |

| Handler_write              | 8492      |

| Key_blocks_not_flushed     | 1         |

| Key_blocks_unused          | -158      |

| Key_blocks_used            | 158       |

| Key_read_requests          | 52672     |

| Key_reads                  | 158       |

| Questions                  | 1394      |

| Table_locks_immediate      | 1392      |

| Threads_cached             | 1         |

| Threads_connected          | -1        |









Any idea any one, that what can be tunned here for keeping sql_thread
running same as other slaves. My key_buffers are set to 1G in cnf file.
Also on this slave, no binary logging is enabled or no slow log is
enabled. And no application is connected. This is purely stand alone
slave for disaster recovery.



Regards,






 

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