nosql - MongoDB中的chunk和extent是什么关系？chunk只是逻辑上的？

Question

MongoDB中的chunk和extent是什么关系？chunk只是逻辑上的？ extent预留空间用完了如何处理？

Answer 1

chunk refers to a continuous segment on the shard key in a shard. The data in a chunk is continuous on the shard key, but it may not exist anywhere in the file. It can be said that it is logical. The two links in the explanation in the official documentation explain how it is used in the entire system. (By the way, official documents are becoming more and more abundant and organized better and better)

extent is a continuous section in the data file, which is considered an implementation detail. It is not directly related to chunk. If you're interested, this slides Understanding MongoDB Storage for Performance and Data Safety are great.