title: How to reduce MongoDB storage space after deleting a large amount of data
body: <p>I have a database in MongoDB, called dump. Currently, it reached 6GB in my server. I decided to delete 90% of data in this database to reduce the disk space it occupied. But after doing that its size is still 6GB, while the true storage size is only 250MB.</p>
  
  <p>I guess this is the design of MongoDB? Is there any convinient way to reduce its size? Thank in advance.</p>