master.info文件不断被截断

Question

我在Red Hat Linux上托管MySQL Ver 14.14，Distrib 5.1.16的两台不同服务器上有一个master-to-master复制设置。当我重新启动其中一台服务器时，从站无法启动。当我执行/ var/lib/mysql目录的列表时，我注意到master.info文件被截断为零，导致MySQL认为复制没有设置。

这里是服务器1的my.cnf：

[client] 
port = 3306 
socket = /var/lib/mysql/mysql.sock 

[mysqldump] 
quick 
max_allowed_packet = 16M 

[mysql] 
no-auto-rehash 

[isamchk] 
key_buffer = 20M 
sort_buffer_size = 20M 
read_buffer = 2M 
write_buffer = 2M 

[myisamchk] 
key_buffer = 20M 
sort_buffer_size = 20M 
read_buffer = 2M 
write_buffer = 2M 

[mysqlhotcopy] 
interactive-timeout 

[mysqld] 
port = 3306 
socket = /var/lib/mysql/mysql.sock 
key_buffer = 16M 
max_allowed_packet = 1M 
table_cache = 64 
sort_buffer_size = 512K 
net_buffer_length = 8K 
myisam_sort_buffer_size = 8M 
log-bin = mysql-bin 
relay-log = mysqld-relay-bin 
relay-log-index = mysqld-relay-bin.index 
server-id = 101 
binlog-format = STATEMENT 
replicate-do-db = foo 
replicate-do-db = bar 
binlog-do-db = foo 
binlog-do-db = bar 
auto_increment_increment = 2 
auto_increment_offset = 1 
master-connect-retry = 2 
sync_binlog = 1 
log-error = mysqld.log 
log-warnings = 2 
wait_timeout = 31536000 
expire_logs_days = 45 

这里是服务器2 my.cnf中：

[client] 
port = 3306 
socket = /var/lib/mysql/mysql.sock 

[mysqldump] 
quick 
max_allowed_packet = 16M 

[mysql] 
no-auto-rehash 

[isamchk] 
key_buffer = 20M 
sort_buffer_size = 20M 
read_buffer = 2M 
write_buffer = 2M 

[myisamchk] 
key_buffer = 20M 
sort_buffer_size = 20M 
read_buffer = 2M 
write_buffer = 2M 

[mysqlhotcopy] 
interactive-timeout 

[mysqld] 
port = 3306 
socket = /var/lib/mysql/mysql.sock 
key_buffer = 16M 
max_allowed_packet = 1M 
table_cache = 64 
sort_buffer_size = 512K 
net_buffer_length = 8K 
myisam_sort_buffer_size = 8M 
log-bin = mysql-bin 
relay-log = mysqld-relay-bin 
relay-log-index = mysqld-relay-bin.index 
server-id = 102 
binlog-format = STATEMENT 
replicate-do-db = foo 
replicate-do-db = bar 
binlog-do-db = foo 
binlog-do-db = bar 
auto_increment_increment = 2 
auto_increment_offset = 2 
master-connect-retry = 2 
sync_binlog = 1 
log-error = mysqld.log 
log-warnings = 2 
wait_timeout = 31536000 
expire_logs_days = 45 

我的设置，像这样每个服务器上的奴隶：

STOP SLAVE ; RESET SLAVE ; CHANGE MASTER TO MASTER_HOST='other_sys', MASTER_USER='repl', MASTER_PASSWORD='super_secret_password', MASTER_PORT=3306, MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=14048 ; 

MASTER_LOG_FILE和MASTER_LOG_POS在上例中是任意的。这样做后，我得到了MySQL从状态如下：

mysql> show slave status \G 
*************************** 1. row *************************** 
       Slave_IO_State: Waiting for master to send event 
        Master_Host: other_sys 
        Master_User: repl 
        Master_Port: 3306 
       Connect_Retry: 2 
       Master_Log_File: mysql-bin.000002 
      Read_Master_Log_Pos: 14048 
       Relay_Log_File: mysqld-relay-bin.000002 
       Relay_Log_Pos: 251 
     Relay_Master_Log_File: mysql-bin.000002 
      Slave_IO_Running: Yes 
      Slave_SQL_Running: Yes 
       Replicate_Do_DB: foo,bar 
      Replicate_Ignore_DB: 
      Replicate_Do_Table: 
     Replicate_Ignore_Table: 
     Replicate_Wild_Do_Table: 
    Replicate_Wild_Ignore_Table: 
        Last_Errno: 0 
        Last_Error: 
       Skip_Counter: 0 
      Exec_Master_Log_Pos: 14048 
       Relay_Log_Space: 407 
       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: 0 
Master_SSL_Verify_Server_Cert: No 
       Last_IO_Errno: 0 
       Last_IO_Error: 
       Last_SQL_Errno: 0 
       Last_SQL_Error: 
1 row in set (0.00 sec) 

我然后执行使用命令reboot服务器的重新启动。重新启动后，MySQL从站有时会从停止的地方自动启动。其他时候，MySQL从服务器根本无法启动，我注意到show slave status \G返回一个空集，并且/var/lib/mysql/master.info文件被截断为零。就好像Linux在重启时没有将文件缓冲区刷新到inode，所以从属信息不会被保存。

我在配置从站时错过了什么吗？

Answer 1

以防万一有人想知道我是如何解决这个：

的问题是Linux的文件缓冲。我执行了上述相同的步骤，除了在拨打reboot之前我拨打sync，并且在10次尝试中100％的时间内工作。没有sync，在我的测试中10次失败了9次。我不知道为什么Linux在关机时没有同步文件缓存，但拨打sync或等待一分钟后再发出reboot已解决问题。