fsimage = name table , which stores all data in namonode, and loads the data into memory at runtime for storage
edits_inprogress is similar to the Log in the LSM tree. During the process of writing to hdfs, it is stored in this file.
When the stored data reaches a certain level/or how long the regular interval is, the content of this file will be updated to the same time when fsimage
starts to write data. Write to the namonode memory and edit.
Immediately reading the data just written is to read the data of the namenode memory and the original fsimage memory.
When the edits data is merged into the fsimage, the data that is read and written will be read and written. Read in fsimage.