随着数据量和访问量的增长，网站构架大致有这么几个发展阶段(以PHP+MysqL+Memcached为例)：

1: PHP + MysqL 2: PHP + MysqL (Master + Slaves) 3: PHP + MysqL (Master + Slaves) + Memcached (Middleware) 4: PHP + MysqL (Sharding + Master + Slaves) + Memcached (Middleware) 5: PHP + MysqL (Sharding + Master + Slaves) + Memcached (Middleware) + Nosql