title: Database size on disk increases as a multiple of the CSV file I mongoimport?
body: <p>I imported a CSV file which is 230M in total size, the dimensions of the file are 3069055 rows and 13 columns.</p>
  
  <p>The command I used to import was:</p>
  
  <p>mongoimport -d taq -c mycollection --type csv --file myfile.csv --headerline </p>
  
  <p>Before I did this import the taq database was empty. After the import completed (which took 4 minutes), I checked the size of the database files in the mongodb user directory. This is what I see:</p>
  
  <pre><code>-rw------- 1 mongod mongod  64M Jul 23 14:13 taq.0  
  -rw------- 1 mongod mongod 128M Jul 23 14:10 taq.1 
  -rw------- 1 mongod mongod 256M Jul 23 14:11 taq.2
  -rw------- 1 mongod mongod 512M Jul 23 14:13 taq.3 
  -rw------- 1 mongod mongod 1.0G Jul 23 14:13 taq.4 
  -rw------- 1 mongod mongod 2.0G Jul 23 14:13 taq.5
  -rw------- 1 mongod mongod  16M Jul 23 14:13 taq.ns
  </code></pre>
  
  <p>Six taq files have been created, numbered from 0 to 5. The total size of these files is multiple GBs. Why is this, when the CSV file I imported is only 230M? Is this a bug? Or am I missing something?</p>
  
  <p>Cheers.</p>