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Priority 0 Replica Set Members 优先级0的次副本不能变成主副本，它不能参与被选举。她保持数据集复制功能、读操作、投票。 A priority 0 member is a secondary that cannot become primary. Priority 0 members cannot trigger elections. Otherwise these members function as normal secondaries. A priority 0 member maintains a copy of the data set, accepts read operations, and votes in elections. Configure a priority 0 member to prevent secondariesfrom becoming primary, which is particularly useful in multi-data center deployments. In a three-member replica set, in one data center hosts the primary and a secondary. A second data center hosts one priority 0 member that cannot become primary.
Priority 0 Members as StandbysA priority 0 member can function as a standby备用. In some replica sets, it might not be possible 不可能 to add a new member in a reasonable amount of time. A standby member keeps a current copy of the data to be able to replace an unavailable member. In many cases, you need not set standby to priority 0. However, in sets with varied hardware （在不同的硬件设置） or geographic distribution （地理分布）, a priority 0 standby ensures that only qualified members become primary. A priority 0 standby may also be valuable for some members of a set with different hardware or workload profiles. In these cases, deploy a member with priority 0 so it can’t become primary. Also consider using anhidden member for this purpose. If your set already has seven voting members, also configure the member as non-voting. Priority 0 Members and FailoverWhen configuring a priority 0 member, consider potential failover patterns （潜在的故障转移模式）, including all possible network partitions. Always ensure that your main data center contains both a quorum of voting members and contains members that are eligible to be primary. ConfigurationTo configure a priority 0 member, see Prevent Secondary from Becoming Primary. |
