title: Migrating data from MongoDB to SQL Server, performance degrades over time
body: <p>I want transfer data from MongoDB to SQL Sever using the C# driver.
  The data size is about 20,000,000 in three collections. I'm using 3 thread to
  read it and 3 threads to insert into 3 different SQL Server tables.</p>
  
  <p>After reading about 70,000,000 documents, the performance becomes
  worse, the speed about one tenth of before, and network
  bandwidth slumps.</p>
  
  <p>How can I prevent performance from dropping off?</p>