What is Diagnostic.data file in MongoDb data folder? I'm trying to create a backup server for my mongodb using the strategy of copying files.

I wonder what is Diagnostic.data folder? Should I copy that too? or I can simply ignore it?

My Diagnostic.data folder size is around 300MB that is bigger than my other database files.

What about journal folder? Can I ignore it too?
The diagnostic.data file contains the result of db.serverStatus() command in binary format. This will be used by the MongoDB engineers to analyze the behavior of the server if any error happens.

It is not necessary to take a backup of this file.