MySQL多实例就是，在一台机器上开启多个不同的服务端口（如：3306,3307,3308...），运行多个MySQL服务进程，这些服务进程通过不同的socket监听不同的端口提供服务。
MySQL可以共用一套安全程序，使用不同的my.cnf配置文件，启动程序，数据文件。
逻辑上是独立的，但是一个实例过载过高的时候会对其他造成影响。
MySQL多实例的作用与问题：
1.有效利用服务器资源
2.节约服务器资源
3.资源互相抢占问题
当某个服务实现并发生很高的或者有慢查询的时候，这个实例会消耗很多的内存。
二.MySQL常见的配置方案
1.多个配置文件，多个启动程序
2.单一配置文件部署方案
三.开始安装
1.安装依赖包
yum -y install ncurses-devel libaio-devel
2.杀掉之前的MySQL进程
pkill mysqld
netstat -ntlp
ps -ef | grep mysql
rm -f /etc/init.d/mysqld
3.创建多实例的目录结构
mkdir -p /data/{3306,3307}/data
tree /data
4.创建多实例的配置文件
多实例启动文件的启动MySQL服务实质：
mysql_safe --defaults-file=/data/3306/my.cnf 2>&1 > /dev/null &
多实例启动文件的关闭MySQL服务实质
mysqladmin -uroot -p*** -S /data/3306/mysql.sock shutdown
my.cnf
[client]
port = 3306
socket = /data/3306/mysql.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /data/3306/mysql.sock
basedir = /application/mysql
datadir = /data/3306/data
open_files_limit = 1024
back_log = 600
max_connections = 800
max_connect_errors = 3000
table_cache = 614
external-locking = FALSE
max_allowed_packet =8M
sort_buffer_size = 1M
join_buffer_size = 1M
thread_cache_size = 100
thread_concurrency = 2
query_cache_size = 2M
query_cache_limit = 1M
query_cache_min_res_unit = 2k
#default_table_type = InnoDB
thread_stack = 192K
#transaction_isolation = READ-COMMITTED
tmp_table_size = 2M
max_heap_table_size = 2M
long_query_time = 1
#log_long_format
#log-error = /data/3306/error.log
#log-slow-queries = /data/3306/slow.log
pid-file = /data/3306/mysql.pid
log-bin = /data/3306/mysql-bin
relay-log = /data/3306/relay-bin
relay-log-info-file = /data/3306/relay-log.info
binlog_cache_size = 1M
max_binlog_cache_size = 1M
max_binlog_size = 2M
expire_logs_days = 7
key_buffer_size = 16M
read_buffer_size = 1M
read_rnd_buffer_size = 1M
bulk_insert_buffer_size = 1M
#myisam_sort_buffer_size = 1M
#myisam_max_sort_file_size = 10G
#myisam_max_extra_sort_file_size = 10G
#myisam_repair_threads = 1
#myisam_recover
lower_case_table_names = 1
skip-name-resolve
slave-skip-errors = 1032,1062
replicate-ignore-db=mysql
server-id = 1
innodb_additional_mem_pool_size = 4M
innodb_buffer_pool_size = 32M
innodb_data_file_path = ibdata1:128M:autoextend
innodb_file_io_threads = 4
innodb_thread_concurrency = 8
innodb_flush_log_at_trx_commit = 2
innodb_log_buffer_size = 2M
innodb_log_file_size = 4M
innodb_log_files_in_group = 3
innodb_max_dirty_pages_pct = 90
innodb_lock_wait_timeout = 120
innodb_file_per_table = 0
[mysqldump]
quick
max_allowed_packet = 2M
[mysqld_safe]
log-error=/data/3306/mysql_qb3306.err
pid-file=/data/3306/mysqld.pid
配置的时候需要注意端口，还有最后的日志需要自己知道在哪，方便排错；再有就是有一个"server-id = 1"最好每个实例的id不要一样。
mysql（启动关闭服务的脚本）
#!/bin/sh
#init
port=3306
mysql_user="root"
mysql_pwd="qb123"
CmdPath="/application/mysql/bin"
mysql_sock="/data/${port}/mysql.sock"
#startup function
function_start_mysql()
{
if [ ! -e "$mysql_sock" ];then
printf "Starting MySQL...\n"
/bin/sh ${CmdPath}/mysqld_safe --defaults-file=/data/${port}/my.cnf 2>&1 > /dev/null &
else
printf "MySQL is running...\n"
exit
fi
}
#stop function
function_stop_mysql()
{
if [ ! -e "$mysql_sock" ];then
printf "MySQL is stopped...\n"
exit
else
printf "Stoping MySQL...\n"
${CmdPath}/mysqladmin -u ${mysql_user} -p${mysql_pwd} -S /data/${port}/mysql.sock shutdown
fi
}
#restart function
function_restart_mysql()
{
printf "Restarting MySQL...\n"
function_stop_mysql
sleep 2
function_start_mysql
}
case $1 in
start)
function_start_mysql
;;
stop)
function_stop_mysql
;;
restart)
function_restart_mysql
;;
*)
printf "Usage: /data/${port}/mysql {start|stop|restart}\n"
esac