Hash 有多个散列环意味着什么？

我在看一段视频，15:04-15:26。 演示者在这里解释twitter将如何为用户提供家庭时间表-

- home timeline is served from redis cluster.
- replication factor is 3 i.e. data is replicated on 3 redis machines
- Timeline service - responsible to serve your home timeline

Steps explained to get home timeline - 

 1. Timeline service needs to find out one machine out of redis machine that has your home timeline.
 2. We are running three different hashrings
 3. We go through each of them and find the one, which is fastest.

我不知道有多个散列环意味着什么？ 这类似于一致性哈希中使用的多个哈希吗