MongoDB 独立与副本集以及如何将数据从独立迁移到副本集

Question

我有一些关于 MongoDB 独立版和副本集的问题，我不太明白。

• 我什么时候应该使用它们中的任何一个
• 为什么所有副本集教程都显示 3 个连接，有原因吗？
• 我可以仅为 1 个实例创建副本集吗？在这种情况下，它与独立的 mongodb 实例有何不同？
• 如何将数据从独立实例迁移到副本集？

我问所有这些问题是因为最近我试图实现事务和 session 只能在“副本集”上启动，我根本不明白其中的区别。

Answer 1

• 我什么时候应该使用它们中的任何一个？

Replication is the process of synchronizing data across multiple servers. Replication provides redundancy and increases data availability with multiple copies of data on different database servers. Replication protects a database from the loss of a single server. Replication also allows you to recover from hardware failure and service interruptions. With additional copies of the data, you can dedicate one to disaster recovery, reporting, or backup.

• To keep your data safe
• High (24*7) availability of data
• Disaster recovery
• No downtime for maintenance (like backups, index rebuilds, compaction) Read scaling (extra copies to read from)
• Replica set is transparent to the application

• 为什么所有副本集教程都显示 3 个连接，有原因吗？

The basic implementation to take full advantage of replication specifies youshould have at least one primary node with two secondary nodes. So theexamples are always with 3 nodes. Not only this if from 3 thePrimary node goes down you still have 2 nodes (mongoDB will assignusing arbiter rule) and one primary and one secondary for high availability

• 我可以仅为 1 个实例创建副本集吗？在这种情况下，它与独立的 mongodb 实例有何不同？

It does not make sense to have single instance with mongo replication.

• 如何将数据从独立实例迁移到副本集？

Convert a Standalone to a Replica Set . Your existing data will be migrated to all replication instances once they are up and running when converted to replication sets from standalone.