一:redis-cluster架构图 
架构细节:
(1)所有的redis节点彼此互联(PING-PONG机制),内部使用二进制协议优化传输速度和带宽.
(2)节点的fail是通过集群中超过半数的节点检测失效时才生效.
(3)客户端与redis节点直连,不需要中间proxy层.客户端不需要连接集群所有节点,连接集群中任何一个可用节点即可
(4)redis-cluster把所有的物理节点映射到[0-16383]slot上,cluster 负责维护node<->slot<->value
Redis 集群中内置了 16384 个哈希槽，当需要在 Redis 集群中放置一个 key-value 时，redis 先对 key 使用 crc16 算法算出一个结果，然后把结果对 16384 求余数，这样每个 key 都会对应一个编号在 0-16383 之间的哈希槽，redis 会根据节点数量大致均等的将哈希槽映射到不同的节点
二:Redis集群的搭建
2.1. 集群搭建环境
1、使用ruby脚本搭建集群。需要ruby的运行环境。
安装ruby
yum install ruby
yum install rubygems
2、安装ruby脚本运行使用的包。
[root@localhost ~]# gem install redis-3.0.0.gem
Successfully installed redis-3.0.0
1 gem installed
Installing ri documentation for redis-3.0.0...
Installing RDoc documentation for redis-3.0.0...
[root@localhost ~]#
[root@localhost ~]# cd redis-3.0.0/src
[root@localhost src]# ll *.rb
-rwxrwxr-x. 1 root root 48141 Apr 1 2015 redis-trib.rb
2.2. 搭建步骤
需要6台redis服务器。搭建伪分布式。
需要6个redis实例。
需要运行在不同的端口7001-7006
第一步：创建6个redis实例，每个实例运行在不同的端口。需要修改redis.conf配置文件。配置文件中还需要把cluster-enabled yes前的注释去掉。 
第二步：启动每个redis实例。
第三步：使用ruby脚本搭建集群。
./redis-trib.rb create --replicas 1 192.168.25.153:7001 192.168.25.153:7002 192.168.25.153:7003 192.168.25.153:7004 192.168.25.153:7005 192.168.25.153:7006创建关闭集群的脚本：
[root@localhost redis-cluster]# vim shutdow-all.sh
redis01/redis-cli -p 7001 shutdown
redis01/redis-cli -p 7002 shutdown
redis01/redis-cli -p 7003 shutdown
redis01/redis-cli -p 7004 shutdown
redis01/redis-cli -p 7005 shutdown
redis01/redis-cli -p 7006 shutdown
[root@localhost redis-cluster]# chmod u+x shutdow-all.sh
[root@localhost redis-cluster]# ./redis-trib.rb create --replicas 1 192.168.25.153:7001 192.168.25.153:7002 192.168.25.153:7003 192.168.25.153:7004 192.168.25.153:7005 192.168.25.153:7006
>>> Creating cluster
Connecting to node 192.168.25.153:7001: OK
Connecting to node 192.168.25.153:7002: OK
Connecting to node 192.168.25.153:7003: OK
Connecting to node 192.168.25.153:7004: OK
Connecting to node 192.168.25.153:7005: OK
Connecting to node 192.168.25.153:7006: OK
>>> Performing hash slots allocation on 6 nodes...
Using 3 masters:
192.168.25.153:7001
192.168.25.153:7002
192.168.25.153:7003
Adding replica 192.168.25.153:7004 to 192.168.25.153:7001
Adding replica 192.168.25.153:7005 to 192.168.25.153:7002
Adding replica 192.168.25.153:7006 to 192.168.25.153:7003
M: 2e48ae301e9c32b04a7d4d92e15e98e78de8c1f3 192.168.25.153:7001
slots:0-5460 (5461 slots) master
M: 8cd93a9a943b4ef851af6a03edd699a6061ace01 192.168.25.153:7002
slots:5461-10922 (5462 slots) master
M: 2935007902d83f20b1253d7f43dae32aab9744e6 192.168.25.153:7003
slots:10923-16383 (5461 slots) master
S: 74f9d9706f848471583929fc8bbde3c8e99e211b 192.168.25.153:7004
replicates 2e48ae301e9c32b04a7d4d92e15e98e78de8c1f3
S: 42cc9e25ebb19dda92591364c1df4b3a518b795b 192.168.25.153:7005
replicates 8cd93a9a943b4ef851af6a03edd699a6061ace01
S: 8b1b11d509d29659c2831e7a9f6469c060dfcd39 192.168.25.153:7006
replicates 2935007902d83f20b1253d7f43dae32aab9744e6
Can I set the above configuration? (type 'yes' to accept): yes
>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join.....
>>> Performing Cluster Check (using node 192.168.25.153:7001)
M: 2e48ae301e9c32b04a7d4d92e15e98e78de8c1f3 192.168.25.153:7001
slots:0-5460 (5461 slots) master
M: 8cd93a9a943b4ef851af6a03edd699a6061ace01 192.168.25.153:7002
slots:5461-10922 (5462 slots) master
M: 2935007902d83f20b1253d7f43dae32aab9744e6 192.168.25.153:7003
slots:10923-16383 (5461 slots) master
M: 74f9d9706f848471583929fc8bbde3c8e99e211b 192.168.25.153:7004
slots: (0 slots) master
replicates 2e48ae301e9c32b04a7d4d92e15e98e78de8c1f3
M: 42cc9e25ebb19dda92591364c1df4b3a518b795b 192.168.25.153:7005
slots: (0 slots) master
replicates 8cd93a9a943b4ef851af6a03edd699a6061ace01
M: 8b1b11d509d29659c2831e7a9f6469c060dfcd39 192.168.25.153:7006
slots: (0 slots) master
replicates 2935007902d83f20b1253d7f43dae32aab9744e6
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
[root@localhost redis-cluster]#
