AWS ElastiCache 集群和 AWS ElastiCache 复制组有什么区别？
What is the difference between AWS ElastiCache Cluster and AWS ElastiCache Replication Group?
在 terraform/cloudformation 文档中，有两种不同的资源可用于创建 ElastiCache Redis 实例：
aws_elasticache_cluster (https://www.terraform.io/docs/providers/aws/r/elasticache_cluster.html) aws_elasticache_replication_group (https://www.terraform.io/docs/providers/aws/r/elasticache_replication_group.html)
这两者有什么区别？我应该选择哪一个？
A replication group is a collection of cache clusters, where one of the clusters is a primary read-write cluster and the others are read-only replicas.
简单来说，复制组是针对Redis集群的，缓存集群是针对Memcache的。您不能将该命令应用于其他人，即 Redis 集群的缓存集群，反之亦然。
redis也可以使用aws_elasticache_cluster但前提是当redis有节点1时，那不是集群模式。
num_cache_nodes – (Required unless replication_group_id is provided) The initial number of cache nodes that the cache cluster will have. For Redis, this value must be 1. For Memcache, this value must be between 1 and 20. If this number is reduced on subsequent runs, the highest numbered nodes will be removed.
在 terraform/cloudformation 文档中，有两种不同的资源可用于创建 ElastiCache Redis 实例：
aws_elasticache_cluster(https://www.terraform.io/docs/providers/aws/r/elasticache_cluster.html)aws_elasticache_replication_group(https://www.terraform.io/docs/providers/aws/r/elasticache_replication_group.html)
这两者有什么区别？我应该选择哪一个？
A replication group is a collection of cache clusters, where one of the clusters is a primary read-write cluster and the others are read-only replicas.
简单来说，复制组是针对Redis集群的，缓存集群是针对Memcache的。您不能将该命令应用于其他人，即 Redis 集群的缓存集群，反之亦然。
redis也可以使用aws_elasticache_cluster但前提是当redis有节点1时，那不是集群模式。
num_cache_nodes – (Required unless replication_group_id is provided) The initial number of cache nodes that the cache cluster will have. For Redis, this value must be 1. For Memcache, this value must be between 1 and 20. If this number is reduced on subsequent runs, the highest numbered nodes will be removed.