这篇文章给大家介绍Mysql MHA部署中什么是主从复制，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。Mysql MHA部署-主从复制架构说明:参考：http://www.zhaibibei.cn/mysql/mha/搭建主从复制1 Mysql安装2 rac1(187 主),rac3(223 从)配置异步复制3 rac1(187 主),rac2(188 从)配置半同步复制我们根据上面的拓扑建立主从关系，192.168.2.223采用半同步，192.168.2.223采用异步采用基于GTID的复制，否则建议关闭GTID功能这里就不多做介绍了，具体见上一个专题注意在做主从同步的时候建议清理下从库相关信息reset master ;reset slave all;时间同步：[root@rac1 ~]# ntpdate cn.pool.ntp.org14 Mar 15:37:01 ntpdate[31863]: step time server 203.107.6.88 offset 2.987670 sec[root@rac1 ~]# dateSat Mar 14 15:37:17 CST 20201 Mysql安装
—rac1(主187),rac2(从188),rac3(从223)分别安装Mysql1.1 配置Limits[root@rac1 package]# cat>>/etc/security/limits.conf
mysql soft nofile 1024mysql hard nofile 65536mysql soft nproc 4095mysql hard nproc 16384mysql soft stack 10240mysql hard stack 32768EOF1.2 系统内核参数shmmax和shmall的设置 shmmax指的是单个内存段的最大值，单位为bytes shmall指的是能使用的最大内存大小，单位为pages, pages大小可通过 getconf PAGE_SIZE 命令查询，一般操作系统page大小为4096 bytes 如操作系统内存为8G，给80%给Oracle使用，则 kernel.shmmax=(8 * 0.8 * 1024 * 1024 * 1024 )=6871947673 kernel.shmall=kernel.shmmax/4096=1677721如默认值比较大 请保持默认值cat>>/etc/sysctl.conf
fs.file-max = 6815744kernel.sem = 250 32000 100 128kernel.shmmni = 4096kernel.shmall = 1073741824kernel.shmmax = 4398046511104fs.aio-max-nr = 1048576# vm.min_free_kbytes = 524288vm.swappiness= 5# vm.nr_hugepages =1024# vm.hugetlb_shm_group = 2000net.core.rmem_default = 262144net.core.rmem_max = 4194304net.core.wmem_default = 262144net.core.wmem_max = 1048576net.ipv4.ip_local_port_range = 1024 655001.3 目录规划目录名称 参数名称 路径地址安装目录 basedir /usr/local/mysql数据文件目录 datadir /data/mysql/data临时文件目录 tmpdir /data/mysql/tmpsocket文件目录 socket /data/mysql/data/mysql.sockbin日志文件目录 log_bin /datalog/mysql/binlogrelay日志文件目录 relay_log /datalog/mysql/relaylog1.4 MySQL5.7下载下载地址：dev.mysql.com/downloads/mysql这里统一使用5.7.28的版本[root@rac1 mysql]# pwd/package/mysql[root@rac1 mysql]# ll -rthtotal 692M-rw-r–r– 1 root root 692M Mar 14 11:49 mysql-5.7.28-linux-glibc2.12-x86_64.tar.gz[root@rac1 mysql]#1.5 新建用户及目录
[root@rac1 ~]# /usr/sbin/groupadd -g 105 mysql[root@rac1 ~]# /usr/sbin/useradd -u 105 -g mysql mysql[root@rac1 ~]# echo “123456” |passwd mysql –stdin[root@rac1 ~]# mkdir -p /data/mysql/software[root@rac1 ~]# mkdir -p /usr/local/mysql[root@rac1 ~]# mkdir -p /data/mysql/data[root@rac1 ~]# mkdir -p /datalog/mysql/binlog[root@rac1 ~]# mkdir -p /datalog/mysql/relaylog[root@rac1 ~]# chown -R mysql:mysql /usr/local/mysql[root@rac1 ~]# mkdir -p /data/mysql/tmp[root@rac1 ~]# chown -R mysql:mysql /data/mysql[root@rac1 ~]# chown -R mysql:mysql /datalog/mysql/1.6 配置环境变量
[root@rac1 ~]# su – mysqlAttempting to create directory /home/mysql/perl5[mysql@rac1 ~]$ vim .bash_profile…export MYSQL_HOME=/usr/local/mysqlexport PATH=$HOME/bin:$MYSQL_HOME/bin:$PATHexport LD_LIBRARY_PATH=$MYSQL_HOME/lib:$LD_LIBRARY_PATH[mysql@rac1 ~]$ source .bash_profile1.7 建立配置文件
[root@rac1 ~]# cp /etc/my.cnf /etc/my.cnf.bak[root@rac1 ~]# vim /etc/my.cnf[mysql]user =password =[mysqld]#—————–MySQL Basic Setting—————–#server-id = 1723161113port = 3306user = mysqlpid-file = mysql.pidcharacter_set_server = utf8mb4default_storage_engine = InnoDBskip_name_resolve = 1lower_case_table_names = 1explicit_defaults_for_timestamp = 1open_files_limit = 65535max_connections = 1000max_connect_errors = 100000basedir = /usr/local/mysqldatadir = /data/mysql/datatmpdir = /data/mysql/tmpsocket = /data/mysql/data/mysql.sockquery_cache_type = 0query_cache_size = 0join_buffer_size = 64Mtmp_table_size = 64Mmax_allowed_packet = 32Mread_buffer_size = 16Mread_rnd_buffer_size = 32Msort_buffer_size = 32Mlog_error_verbosity=2log_timestamps=SYSTEM#—————–MySQL Log Setting—————–#log_error = mysql-error.loglog_bin = /datalog/mysql/binlog/mysql-bin.logslow_query_log_file = mysql-slow.logrelay_log = /datalog/mysql/relaylog/mysql-relay.loglog_slave_updates = 1sync_binlog = 1relay_log_recovery = 1binlog_format = rowexpire_logs_days = 14slow_query_log = 1long_query_time = 2log_queries_not_using_indexes = 1log_throttle_queries_not_using_indexes = 10log_slow_admin_statements = 1log_slow_slave_statements = 1min_examined_row_limit = 1000#—————–MySQL Replication Setting—————–#slave_skip_errors = ddl_exist_errorsmaster_info_repository = TABLErelay_log_info_repository = TABLE#gtid_mode = on#enforce_gtid_consistency = 1binlog_rows_query_log_events = 1#—————–MySQL InnoDB Setting—————–#innodb_page_size = 16384innodb_buffer_pool_size = 25600Minnodb_data_file_path = ibdata1:1G:autoextendinnodb_buffer_pool_instances = 8innodb_file_per_table = 1innodb_buffer_pool_load_at_startup = 1innodb_buffer_pool_dump_at_shutdown = 1innodb_flush_log_at_trx_commit = 1innodb_lock_wait_timeout = 5innodb_io_capacity = 800innodb_io_capacity_max = 2000innodb_flush_method = O_DIRECTinnodb_file_format = Barracudainnodb_file_format_max = Barracudainnodb_undo_logs = 128innodb_undo_tablespaces = 3innodb_flush_neighbors = 1innodb_log_file_size = 2Ginnodb_log_buffer_size = 16777216innodb_print_all_deadlocks = 1innodb_strict_mode = 1innodb_sort_buffer_size = 67108864#—————–MySQL semi Replication Setting—————–##plugin_dir = /usr/local/mysql/lib/plugin#plugin_load = “rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so”#loose_rpl_semi_sync_master_enabled = 1#loose_rpl_semi_sync_slave_enabled = 1#loose_rpl_semi_sync_master_timeout = 5000修改my.cnf权限[root@rac1 ~]# chown mysql.mysql /etc/my.cnf1.8 依赖包检查
[root@rac1 ~]# rpm -qa libaio*libaio-0.3.109-13.el7.x86_64libaio-devel-0.3.109-13.el7.x86_64[root@rac1 ~]# rpm -qa lvm2-*lvm2-libs-2.02.177-4.el7.x86_64lvm2-python-libs-2.02.177-4.el7.x86_641.9 解压文件[root@rac1 ~]# chown mysql.mysql /package/mysql -R[mysql@rac1 ~]$ cd /package/mysql/[mysql@rac1 mysql]$ lsmysql-5.7.28-linux-glibc2.12-x86_64.tar.gz[mysql@rac1 mysql]$ tar -zxvf mysql-5.7.28-linux-glibc2.12-x86_64.tar.gz -C /usr/local/mysql/ –strip-components=1mysql-5.7.28-linux-glibc2.12-x86_64/bin/myisam_ftdumpmysql-5.7.28-linux-glibc2.12-x86_64/bin/myisamchkmysql-5.7.28-linux-glibc2.12-x86_64/bin/myisamlog……1.10 配置服务文件这里将mysql.server文件拷贝值init.d目录使其可以当作服务启停[root@rac1 ~]# cp /usr/local/mysql/support-files/mysql.server /etc/init.d/mysqld这里修改下面几处[root@rac1 ~]# vim /etc/init.d/mysqldbasedir=/usr/local/mysqldatadir=/data/mysql/datalockdir=’/data/mysql/data’mysqld_pid_file_path=/data/mysql/data/mysql.pid1.11 初始化数据库[mysql@rac1 mysql]$ /usr/local/mysql/bin/mysqld –defaults-file=/etc/my.cnf –initialize –user=mysql[root@rac1 ~]# tail -f /data/mysql/data/mysql-error.log……2020-03-14T13:22:12.786017+08:00 1 [Note] A temporary password is generated for root@localhost: 7DO4gs27;YOM1.12 启动和关闭数据库[mysql@rac1 mysql]$ /usr/local/mysql/bin/mysqld_safe –defaults-file=/etc/my.cnf –user=mysql &[1] 186422020-03-14T05:24:05.258268Z mysqld_safe Logging to ‘/data/mysql/data/mysql-error.log’.2020-03-14T05:24:05.320993Z mysqld_safe Starting mysqld daemon with databases from /data/mysql/data[mysql@rac1 mysql]$ netstat -lntp|grep mysqld(Not all processes could be identified, non-owned process infowill not be shown, you would have to be root to see it all.)tcp6 0 0 :::3306 :::* LISTEN 19567/mysqld后续可以使用如下命令启停数据库[mysql@rac1 mysql]$ service mysqld stopShutting down MySQL….2020-03-14T05:25:16.603331Z mysqld_safe mysqld from pid file /data/mysql/data/mysql.pid ended[ OK ][1]+ Done /usr/local/mysql/bin/mysqld_safe –defaults-file=/etc/my.cnf –user=mysql[mysql@rac1 mysql]$ service mysqld startStarting MySQL………[ OK ]设置MySQL自启动chkconfig mysqld on1.13 连接数据库默认密码在error文件中有[mysql@rac1 mysql]$ cat /data/mysql/data/mysql-error.log |grep password2020-03-14T13:22:12.786017+08:00 1 [Note] A temporary password is generated for root@localhost: 7DO4gs27;YOM使用如下命令连接[mysql@rac1 mysql]$ mysql -S /data/mysql/data/mysql.sock -uroot -pEnter password: 7DO4gs27;YOMWelcome to the MySQL monitor. Commands end with ; or g.Your MySQL connection id is 6Server version: 5.7.28-logCopyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type ‘help;’ or ‘h’ for help. Type ‘c’ to clear the current input statement.mysql> show databases;ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.mysql> alter user ‘root’@’localhost’ identified by ‘123456’;Query OK, 0 rows affected (0.00 sec)[mysql@rac1 mysql]$ mysql -S /data/mysql/data/mysql.sock -uroot -p123456mysql: [Warning] Using a password on the command line interface can be insecure.Welcome to the MySQL monitor. Commands end with ; or g.Your MySQL connection id is 7Server version: 5.7.28-log MySQL Community Server (GPL)Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type ‘help;’ or ‘h’ for help. Type ‘c’ to clear the current input statement.mysql> show databases;+——————–+| Database |+——————–+| information_schema || mysql || performance_schema || sys |+——————–+4 rows in set (0.00 sec)2 rac1(187 主),rac3(223 从)配置异步复制这节我们的内容为MySQL的复制，MySQL复制有两种形式基于二进制日志文件位置基于GTID这节为第一种基于二进制日志文件位置2.1 开启二进制日志功能无论是使用哪种方式我们都需要启用二进制日志功能如果未开启则需要在my.cnf文件中加入如下参数，需要重启数据库生效—主库187 rac1[mysqld]server-id = 1binlog_format = rowlog_bin = /datalog/mysql/binlog/mysql-bin.logexpire_logs_days = 14log-slave-updates=ON—从库223 rac3[mysqld]server-id = 3binlog_format = rowlog_bin = /datalog/mysql/binlog/mysql-bin.logexpire_logs_days = 14log-slave-updates=ONread_only=1—重启mysql[mysql@rac1 ~]$ service mysqld stopShutting down MySQL…..[ OK ][mysql@rac1 ~]$ service mysqld startStarting MySQL…………..[ OK ]2.2 查看UUID是否一致需要注意的是如果从库是由主库克隆而来，这时的uuid是一样的，这样也会报错该文件位于daadir的auto.cnf文件中vim /data/mysql/data/auto.cnf如果一样可删除该文件后重新启动数据库即可，这时会生成一个新的文件2.3 建立复制账号接下来我们建立一个独立的用于复制的账号主库和从库[mysql@rac1 ~]$ mysql -S /data/mysql/data/mysql.sock -uroot -pmysql> CREATE USER ‘repl’@’192.168.2.187’ IDENTIFIED BY ‘rpl’;mysql> GRANT REPLICATION SLAVE ON *.* TO ‘repl’@’192.168.2.187’;mysql> CREATE USER ‘repl’@’192.168.2.223’ IDENTIFIED BY ‘rpl’;mysql> GRANT REPLICATION SLAVE ON *.* TO ‘repl’@’192.168.2.223’;mysql> flush privileges;mysql> select host,user from user;+—————+—————+| host | user |+—————+—————+| 192.168.2.187 | repl || 192.168.2.223 | repl || localhost | mysql.session || localhost | mysql.sys || localhost | root |+—————+—————+5 rows in set (0.00 sec)这里我们限制该账号只能从同步的两台服务器上连接2.4 备份主库—创建测试数据(模拟生产数据)mysql> CREATE DATABASE jumptest DEFAULT CHARSET utf8 COLLATE utf8_general_ci;Query OK, 1 row affected (0.00 sec)mysql> use jumptestDatabase changedmysql> source /package/mysql/jumpserver_bak_2020_03_13_22_00_01.sql—备份[mysql@rac1 ~]$ mysqldump -S /data/mysql/data/mysql.sock -uroot -p –databases jumptest –single-transaction –master-data=2 –set-gtid-purged=off –triggers –events –routines> /tmp/dumpmaster.sqlEnter password:[mysql@rac1 ~]$ ll -rth /tmp/dumpmaster.sql-rw-r–r– 1 mysql mysql 19M Mar 14 17:04 /tmp/dumpmaster.sql2.5 文件传输接下来将主库的dump文件传到备份，之后更改备库的文件权限主库[mysql@rac1 ~]$ scp /tmp/dumpmaster.sql root@192.168.2.223:/tmp从库[root@rac3 ~]# chown mysql:mysql /tmp/dumpmaster.sql2.6 备库导入数据接下来我们将备份的数据导入到备份[mysql@rac3 ~]$ mysql -S /data/mysql/data/mysql.sock -uroot -pEnter password:Welcome to the MySQL monitor. Commands end with ; or g.Your MySQL connection id is 3Server version: 5.7.28-log MySQL Community Server (GPL)Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type ‘help;’ or ‘h’ for help. Type ‘c’ to clear the current input statement.mysql> CREATE DATABASE jumptest DEFAULT CHARSET utf8 COLLATE utf8_general_ci;Query OK, 1 row affected (0.01 sec)mysql> use jumptestDatabase changedmysql> source /tmp/dumpmaster.sql2.7 开始同步接下来我们开启同步首先我们查看dumpmaster.sql文件中master的信息mysql> show master status;+——————+———-+————–+——————+——————————————–+| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |+——————+———-+————–+——————+——————————————–+| mysql-bin.000004 | 34751569 | | | c1227971-65b3-11ea-bf67-080027839e5c:1-297 |+——————+———-+————–+——————+——————————————–+1 row in set (0.00 sec)—从库开启同步命令2.223mysql> change master to master_host=’192.168.2.187′, master_user=’repl’, master_password=’rpl’,master_log_file=’mysql-bin.000004′,master_log_pos= 34751569;Query OK, 0 rows affected, 2 warnings (0.03 sec)mysql> start slave;Query OK, 0 rows affected (0.00 sec)2.8 从库查看同步状态使用如下命令查看同步是否正常主要关注如下几点Slave_IO_Running需要为YESSlave_SQL_Running需要为YESSeconds_Behind_Master需要为0mysql> show slave statusG*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.2.187 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 34751569 Relay_Log_File: mysql-relay.000002 Relay_Log_Pos: 320 Relay_Master_Log_File: mysql-bin.000004 Slave_IO_Running: Yes Slave_SQL_Running: Yes …… Seconds_Behind_Master: 0……2.9 重启和重置复制使用如下命令关闭重启mysql>stop slave;mysql>start slave;我们可以独立的重启IO进程或者SQL进程mysql>stop slave sql_thread;mysql>stop slave io_thread;mysql>start slave io_thread;mysql>start slave sql_thread;使用如下命令重置复制mysql>reset slave all;3 rac1(187 主),rac3(188 从)配置半同步复制3.1 半同步介绍异步的复制，主库将二进制日志发送到从库后并不需要确认从库是否接受并应用，这时就可能会造成数据丢失。MySQL 从5.5版本后推出了半同步的功能，相当于Oracle DG的最大保护模式，它要求从库在接收并应用日志后，主库才提交完成，保证了数据。开启半同步需要如下要求：MySQL 5.5及以上版本变量have_dynamic_loading为YES3.2 188从库初始化主库数据188：mysql> CREATE DATABASE jumptest DEFAULT CHARSET utf8 COLLATE utf8_general_ci;Query OK, 1 row affected (0.01 sec)mysql> use jumptestDatabase changedmysql> source /tmp/dumpmaster.sql3.3 创建复制账号[mysql@rac1 ~]$ mysql -S /data/mysql/data/mysql.sock -uroot -pmysql> CREATE USER ‘repl’@’192.168.2.187’ IDENTIFIED BY ‘rpl’;mysql> GRANT REPLICATION SLAVE ON *.* TO ‘repl’@’192.168.2.187’;mysql> CREATE USER ‘repl’@’192.168.2.188’ IDENTIFIED BY ‘rpl’;mysql> GRANT REPLICATION SLAVE ON *.* TO ‘repl’@’192.168.2.188’;mysql> flush privileges;mysql> use mysql—从库188mysql> select host,user from user;+—————+—————+| host | user |+—————+—————+| 192.168.2.187 | repl || 192.168.2.188 | repl || localhost | mysql.session || localhost | mysql.sys || localhost | root |+—————+—————+5 rows in set (0.00 sec)—主库187mysql> select host,user from user;+—————+—————+| host | user |+—————+—————+| 192.168.2.187 | repl || 192.168.2.188 | repl || 192.168.2.223 | repl || localhost | mysql.session || localhost | mysql.sys || localhost | root |+—————+—————+6 rows in set (0.00 sec)3.4 加载半同步插件因需执行INSTALL PLUGIN, SET GLOBAL, STOP SLAVE和START SLAVE操作，所以用户需有SUPER权限主库和从库mys开发云主机域名ql> INSTALL PLUGIN rpl_semi_sync_master SONAME ‘semisync_master.so’;mysql> INSTALL PLUGIN rpl_semi_sync_slave SONAME ‘semisync_slave.so’;这里安装半同步的master和slave插件考虑到后面主从可能需要切换，这里在主从库上都安装确认是否加载成功mysql> show plugins;……| rpl_semi_sync_master | ACTIVE | REPLICATION | semisync_master.so | GPL || rpl_semi_sync_slave | ACTIVE | REPLICATION | semisync_slave.so | GPL |+—————————-+———-+——————–+——————–+———+mysql> SELECT PLUGIN_NAME, PLUGIN_STATUS FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME LIKE ‘%semi%’;+———————-+—————+| PLUGIN_NAME | PLUGIN_STATUS |+———————-+—————+| rpl_semi_sync_master | ACTIVE || rpl_semi_sync_slave | ACTIVE |+———————-+—————+2 rows in set (0.00 sec)3.5 启用半同步首先我们启用半同步插件主库 187mysql> SET GLOBAL rpl_semi_sync_master_enabled = 1;从库 188mysql> SET GLOBAL rpl_semi_sync_slave_enabled = 1;mysql> change master to master_host=’192.168.2.187′, master_user=’repl’, master_password=’rpl’,master_log_file=’mysql-bin.000004′,master_log_pos= 34752186;mysql> start slave;mysql> show slave status G;之后需要重启IO线程才能使半同步生效，也可直接重启复制从库mysql> STOP SLAVE IO_THREAD;mysql> START SLAVE IO_THREAD;如果从库超过一定时间不能和主库进行通信，则会自动降为异步模式该时间由rpl_semi_sync_master_timeout参数控制，单位为毫秒3.6 查看半同步状态我们使用如下命令查看半同步是否正常工作主库的master和从库的slave都需要为ON主库mysql> show status like ‘Rpl_semi_sync_master_status’;+—————————–+——-+| Variable_name | Value |+—————————–+——-+| Rpl_semi_sync_master_status | ON |+—————————–+——-+1 row in set (0.02 sec)mysql> show status like ‘Rpl_semi_sync_slave_status’;+—————————-+——-+| Variable_name | Value |+—————————-+——-+| Rpl_semi_sync_slave_status | OFF |+—————————-+——-+1 row in set (0.00 sec)从库mysql> show status like ‘Rpl_semi_sync_slave_status’;+—————————-+——-+| Variable_name | Value |+—————————-+——-+| Rpl_semi_sync_slave_status | ON |+—————————-+——-+1 row in set (0.00 sec)mysql> show status like ‘Rpl_semi_sync_master_status’;+—————————–+——-+| Variable_name | Value |+—————————–+——-+| Rpl_semi_sync_master_status | OFF |+—————————–+——-+1 row in set (0.01 sec)3.7 写入配置文件接下来我们将命令写在配置文件中以使重启后自动启动考虑到后面主从可能需要切换，这里在主从库上半同步的master和slave都设置为启动主库187和从库188[mysql@rac1 ~]$ vim /etc/my.cnf#—————–MySQL semi Replication Setting—————–#plugin_dir = /usr/local/mysql/lib/pluginplugin_load = “rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so”rpl_semi_sync_master_enabled = 1rpl_semi_sync_slave_enabled = 1rpl_semi_sync_master_timeout = 5000–从库 188,223mysql> stop slave;Query OK, 0 rows affected (0.00 sec)主187、从库188 重启生效：[mysql@rac1 ~]$ service mysqld restartShutting down MySQL….[ OK ]Starting MySQL………[ OK ]测试数据同步主库187mysql> create table cjc01(id int);Query OK, 0 rows affected (0.01 sec)mysql> insert into cjc01 values(1);Query OK, 1 row affected (0.02 sec)mysql> insert into cjc01 values(2);Query OK, 1 row affected (0.00 sec)mysql> insert into cjc01 values(3);Query OK, 1 row affected (0.01 sec)mysql> update cjc01 set id=100 where id=1;Query OK, 1 row affected (0.01 sec)Rows matched: 1 Changed: 1 Warnings: 0mysql> delete from cjc01 where id=2;Query OK, 1 row affected (0.00 sec)mysql> select * from cjc01;+——+| id |+——+| 100 || 3 |+——+2 rows in set (0.00 sec)从库188mysql> select * from cjc01;+——+| id |+——+| 100 || 3 |+——+2 rows in set (0.00 sec)从库223mysql> select * from cjc01;+——+| id |+——+| 100 || 3 |+——+2 rows in set (0.00 sec)关于Mysql MHA部署中什么是主从复制就分享到这里了，希望以上内容可以对大家有一定的帮助，可以学到更多知识。如果觉得文章不错，可以把它分享出去让更多的人看到。
这篇文章主要介绍了MySQL怎样选择合适的索引，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。先来看一个栗子如果用name索引查找数据需要遍历name字段联合索引树，然后根据遍历出来的主键值去主键…
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