I am using mongodb 3.4 with storage engine wired tiger.when i check every day of storage consumed by mongodb ,i found journal directory size increase everyday. Currently it's size is 1.8Gb.
From Mongo DB document

WiredTiger journal files for MongoDB have a maximum size limit of approximately 100 MB. Once the file exceeds that limit, WiredTiger creates a new journal file.

WiredTiger automatically removes old journal files to maintain only the files needed to recover from last checkpoint.

WiredTiger will pre-allocate journal files.

I want to know why this size increased up to this level ? .why old files not removed ?