title: How to mongorestore 2.6.11 dump to 3.2.5 system?
body: <p>I've noticed an anomaly after performing a <code>mongorestore</code> from a <code>2.6.11</code> dump (from another system) to a <code>3.2.5</code> system.  In a nutshell, the names of the collection files on the <em>new</em> system (in <code>/var/lib/mongodb</code>) are named differently and follow this format:  </p>
  
  <pre><code>collection-55--6670716476518949126.wt
  index-1--6670716476518949126.wt
  </code></pre>
  
  <p>Whereas on the old system, the collections were in <code>/home/mongodb</code> and followed this naming convention:</p>
  
  <pre><code>collection_name.0
  collection_name.1
  collection_name.ns
  </code></pre>
  
  <p>Strangely, everything seems to be "working" though, even though the ~150MB collection file sizes on the old system aren't represented in the new collection file sizes (which are ~150kb).  </p>
  
  <p>I was following the answer in:</p>
  
  <p><a href="https://askubuntu.com/a/643253/367134">How to migrate MongoDB 2.6 to 3.0 with WiredTiger</a></p>
  
  <p>Which basically suggests:  </p>
  
  <ul>
  <li>Perform <code>mongodump</code>.   </li>
  <li>Stop <code>mongod</code></li>
  <li>Upgrade MongoDB version</li>
  <li>Convert the old config file at <code>/etc/mongod.conf</code> to the new YAML format.</li>
  <li>Restart <code>mongod</code></li>
  <li>Perform the <code>mongorestore</code> on the dump.  </li>
  </ul>
  
  <p>As I am doing a <code>mongorestore</code> to a fresh MongoDB 3.2.5 install, however, I already have a config file in the YAML format (see below).  </p>
  
  <p>So the only step it seems I need to do is the <code>mongorestore</code> - which I have done and resulted in the anomalies noted above.  </p>
  
  <p><strong>My questions are:</strong></p>
  
  <p>01) Are there any other steps I should have performed?  </p>
  
  <p>02) Are these file naming 'anomalies' expected?  </p>
  
  <p>03)  Why is there such a large discrepancy in collection file sizes?  </p>
  
  <p>I ask in order to avoid any problems that may arise later due to missing an important step.  </p>
  
  <p><strong>/etc/mongod.conf</strong></p>
  
  <pre><code># mongod.conf
  
  # for documentation of all options, see:
  #   http://docs.mongodb.org/manual/reference/configuration-options/
  
  # Where and how to store data.
  storage:
    dbPath: /var/lib/mongodb
    journal:
      enabled: true
  #  engine:
  #  mmapv1:
  #  wiredTiger:
  
  # where to write logging data.
  systemLog:
    destination: file
    logAppend: true
    path: /var/log/mongodb/mongod.log
  
  # network interfaces
  net:
    port: 27017
    bindIp: 127.0.0.1
  
  
  #processManagement:
  
  #security:
  
  #operationProfiling:
  
  #replication:
  
  #sharding:
  
  ## Enterprise-Only Options:
  
  #auditLog:
  
  #snmp:
  </code></pre>