In cloudera blog we read the following:
"The SecondaryNameNode periodically compacts the EditLog into a “checkpoint;” the EditLog is then cleared. A restart of the NameNode then involves loading the most recent checkpoint and a shorter EditLog containing only events since the checkpoint"
Also in other web page:
"when checkpoint will be created, the secondary node sends fsimage and edit files to name node"
I have some questions and maybe you can link me some resources/books to read the following details: