Load-adaptive replication • two-tier partial replication in ec. Store – 每个数据对象关联 primary copy、secondary and slave replicas. – 复制过程: • first tier : primary copy 和secondary copy. • second tier: 对于popular data objects 复制slave replicas。 帮助改善频繁访问对象的负载; 解决 了负载的突然改变。 11 two-tier replication: The dangers of replication and a solution. In SIGMOD, 1996