1:redis主从环境，均未开启持久化； 当主实例宕机，从实例上的数据不受影响； 当主恢复后，主实例上的数据将会继续同步到从实例，即原来的值将变为空值；
2：redis主从环境，从实例开启快照持久化 当主实例宕机，从实例上的数据不受影响； 当主恢复后，主实例上的数据将会继续同步到从实例，即原来的值将变为空值；
| [ root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 info |grep -A 3 'Replication' # Replication role:master connected_slaves:1 slave0:192.168.1.113,6379,online [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> set 1 a OK redis 192.168.1.112:6379> get 1 "a" [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 shutdown [root@server12 ~]# tail -f /var/log/messages Dec 3 15:27:34 server12 redis[32151]: Connecting to MASTER... Dec 3 15:27:34 server12 redis[32151]: MASTER <-> SLAVE sync started Dec 3 15:27:34 server12 redis[32151]: Error condition on socket for SYNC: Connection refused [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 "a" [root@server11 ~]# /usr/local/redis2/bin/redis-server /usr/local/redis2/etc/redis.conf [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> get 1 (nil) redis 192.168.1.112:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 (nil) |
| [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> get 1 (nil) redis 192.168.1.112:6379> set 1 a OK redis 192.168.1.112:6379> set 2 b OK redis 192.168.1.112:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 shutdown [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 "a" redis 192.168.1.113:6379> get 2 "b" redis 192.168.1.113:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> get 1 (nil) redis 192.168.1.112:6379> get 2 (nil) redis 192.168.1.112:6379> exit [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 (nil) redis 192.168.1.113:6379> get 2 (nil) redis 192.168.1.113:6379> exit |
3：推进一层，当主，从实例均宕机的情况下会如何呢？
| [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> set 1 a OK redis 192.168.1.112:6379> set 2 b OK redis 192.168.1.112:6379> set 3 c OK redis 192.168.1.112:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 "a" redis 192.168.1.113:6379> get 2 "b" redis 192.168.1.113:6379> get 3 "c" redis 192.168.1.113:6379> exit 这次先关闭从实例，再关闭主实例！启动则先启动从实例，测试数据；再启动主实例，再测试数据！ [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 shutdown [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 shutdown [root@server12 ~]# /usr/local/redis2/bin/redis-server /usr/local/redis2/etc/redis.conf [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 "a" redis 192.168.1.113:6379> get 2 "b" redis 192.168.1.113:6379> get 3 "c" [root@server11 ~]# /usr/local/redis2/bin/redis-server /usr/local/redis2/etc/redis.conf [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> get 1 (nil) redis 192.168.1.112:6379> get 2 (nil) redis 192.168.1.112:6379> get 3 (nil) redis 192.168.1.112:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 1 (nil) redis 192.168.1.113:6379> get 2 (nil) redis 192.168.1.113:6379> get 3 (nil) redis 192.168.1.113:6379> exit |
实践证明，在redis主从读写分离条件下，快照持久化只有开在主实例侧才可以保证数据可以跨越实例重启！
| [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 redis 192.168.1.112:6379> set 1 a OK redis 192.168.1.112:6379> set 2 b OK redis 192.168.1.112:6379> set 3 c OK redis 192.168.1.112:6379> set 4 d OK redis 192.168.1.112:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 redis 192.168.1.113:6379> get 4 "d" redis 192.168.1.113:6379> exit [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 shutdown [root@server12 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 shutdown [root@server11 ~]# /usr/local/redis2/bin/redis-server /usr/local/redis2/etc/redis.conf [root@server12 ~]# /usr/local/redis2/bin/redis-server /usr/local/redis2/etc/redis.conf [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.112 -a 123 get 4 "d" [root@server11 ~]# /usr/local/redis2/bin/redis-cli -h 192.168.1.113 -a 123 get 4 "d" |